The Berserk disadvantage in GURPS is an interesting one. It's both a blessing and a curse. It's a blessing in that once you go berserk, you're extremely hard to stop and you can shrug off things most combatants can't. On the other hand, your tactical choices get cut down from "how do I want to balance offense and defense?" to "which suicidally crazy offense-only tactic do I want to use?"
The short version of Berserk is:
- you always All-Out Attack.
- no stunning or shock penalties (and no stun means no knockdown, although you can still suffer knockback)
- you're at +4 to stay conscious or alive.
If you're sufficiently wounded and survive it, you can go berserk. Or if you have Battle Fury, you start every fight berserk.
How to fight as a berserker is a whole other post. Today, let's fight against one. Or more than one - a lot of this advice may seem silly in a party vs. one berserker fight. But what if it's 396 of them? Suddenly you really need to focus on "Can I kill him in one second, or do I need to disable him now and finish him later?"
So what do you do if you're fighting a berserker?
He can't defend, so he's wide open. Your first problem is hitting.
First and foremost, you are going to Telegraphic Attack. The is no reason not to do this. Against someone who is pathologically unable to defend, it's essentially a free +4 to hit. Take it, and use it. It won't increase your chances of a critical hit (and thus possibly some bonus damage effects) but you don't need to main benefit of a critical, anyway - he's already not defending.
All of the below assumes you are using GURPS Martial Arts and Telegraphic Attack. If not, you're much less likely to hit.
Don't worry so much about criticals, just make sure you hit. A miss versus someone who is using All-Out Attack is as close to pure waste as anything can be in a GURPS combat.
Next, you have to put him down. You can't stun a berserker, or knock him down with a high-damage attack. With a +4 to consciousness checks, even a HT 10 berserker is likely to stay awake (and has a 50/50 shot of doing so even at -4xHP!) And it's not exactly common, in my games at least, for berserkers to run around with only HT 10. So your best bet is to a) utterly destroy his ability to attack you or b) put him down to -5xHP.
Here are some options for putting a Berserk opponent down as soon as possible. If you think you've either got a good shot at one-shotting him, or you really only have one chance to do it before you're in a world of hurt yourself, go with a first-tier attack.
These are what I consider the best options, if you can avail yourself of them, to put a berserker down for the count. These can kill.
Eye Shot - if you can pull this off, the eye shot is your best shot. It's -9, -10 if he's wearing appropriate armor, but if it lands you're bypassing 2 DR from the skull, getting an easy freebie cripple on the way. A crippled eye gives the berserker One Eye, which is a -1 in melee combat on subsequent turns.
In any case, hits to the Skull have a x4 injury multiplier for most attack types. So even a mere 2-3 points of damage to the eye is going to inflict 8-12 points of injury and a Major Wound to the berserker. For most folks, this is a -10 roll vs. stunning and knockdown, but a berserker ignores that totally. All you're doing here is reducing the chances of successful retaliation (he's blind in an eye, probably) and accumulating damage needed for force consciousness and death rolls. The sooner you get him down to -5xHP, the better, if you don't want to deal with this guy again.
If you're crazy-good, do two Telegraphic eye shots at a net -5/-5 or -6/-6, plus your Rapid Strike penalties (-3 or -6, depending on Weapon Master, Trained By A Master, and availability of Extra Effort in Combat). If you get both, he's probably getting Blindness, just in case he's somehow still standing.
Skull Shot - A -7 to hit (nets to -3 with Telegraphic Attack). Much easier than the eye, and the same x4 injury multiplier, but any berserker who planned ahead will heave a heavy helmet - a pot helm or great helm over a mail coif is a common choice in my games, because layered head armor isn't that heavy nor does it give you a DX penalty. Plus, the skull comes with DR 2 of its own. Still, if you have a high-damage attack and/or an opponent with insufficient head armor, it's a good target. The x4 injury multiplier means potentially a lot of injury, and you need to put a lot of hurt on.
(Designer's Note - this is one reason the Gladiator Ape in DFM1 has a helmet - it helps head butts and gives it some DR versus the old "I just chop its head in half!" move. Every little bit helps when you're berserk.)
Vitals is the target of choice for impaling attacks if Eyes are too hard. It's only -3, or a net +1 with Telegraphic Attack (and a miss by 1 hits the body, anyway!) The x3 injury multiplier and no cap on damage means a good stab to the vitals can finish a lightly-armored beserker. It's a great choice for piercing attacks, too.
Torso may seem odd as a prime location, but it's less odd than it seems. For a high-damage attack or a lightly-armored defender, or a low-skilled attacker, it's a great choice of locations. -0 to hit plus a Telegraphic Attack is a net +4 to hit, which can go a long way toward negating a lot of penalties for lighting, shock, or bad footing. Plus, no damage is wasted. If you meet the right criteria (can't hit something better and can inflict a lot of damage), it's a very solid choice.
Neck is a pretty good choice for a cutting attack. It's -5 to hit, net -1 with Telegraphic Attack, and cutting gets a x2 injury multiplier. However, it's often well-protected, so it's not quite as good as Skull or Eye, but nearly as hard to hit as skull. Still, you might be able to get in a solid hit at -1 but not at -3 for skull, or he might have armored the hell out of his skull but not his neck.
Veins and Arteries are a good choice as well - only -5 (net -1) and -8 (net -4) for limbs or neck, and they ignore HP limits! This is excellent as you don't want to waste any damage to a berserker. Remember, a good berserker, for you, is one at -5xHP and not getting any more rolls to stay up.
If those don't work for you for some reason, here is where I'd look next. They've good but they can't (generally) kill the berserker outright. They are also useful if you're dead certain you can't finish him in one blow and at least need a shot at reducing his combat viability. These generally won't finish the job but they'll make it harder for him to kill you after you're done hitting him.
Spine is -8 to hit (net -4), but it's got an extra DR 3 under that for the torso, which generally isn't so bad. And while a berserker who takes more than HP in damage to it can ignore the automatic stunning, he can't ignore Bad Back and Paraplegic. If you've got a very high damage attack and want to cripple both legs in one go and you're behind him, take a look at this one. This one can kill outright, but it's tough to do enough damage in one blow to do so.
Legs - Cripple him! One suggestion is to go for the legs. It's only -2 to hit, and if you inflict over HP/2 he goes down in a heap.
I think this is a good but second-rate choice because the berserker isn't out of the fight, but merely fighting prone. This will severely limit him (see Python, M., "I'll bite your legs off!"), but your work isn't done yet. For some berserkers (Gladiator Apes, I'm looking at you again) merely putting them to the floor doesn't do much besides change their movement mode from "run" to "crawl" and they're still dangerous. They still deny an area of the battlefield where you're worried about something grabbing your legs, chopping at your from below, and otherwise keeping up some offense from what otherwise seems like a weak position.
Arms Crippling the arms is a good idea, if this will also disarm the berserker (or partly disarm him, either way). Again, you're reducing his ability to deal damage out but he's still a factor in the fight. This is more useful against a berserker with a two-handed weapon than a one-handed weapon or two weapons (or more than two, in the right sort of game). Taking out one limb makes the weapon that much less useful and might force a default roll to try using it one-handed, probably with additional penalties for being below the weapon's ST score.
Extremities If you can hit him with straight-up skill, this is a pretty good option for either knocking the berserker down or disarming his attacks. It's -4 to hit but a net -0 with Telegraphic Attack. It's got the same downsides as the limbs, and in fact the lower crippling threshold means more damage gets wasted. A berserk humanoid with a pair of crippled hands can still elbow strike, head butt, and kick, and isn't going to be close to death from accumulated HP. He won't even be making consciousness rolls.
Chinks in Armor lets you target weapon points at -8 or -10, depending on where. Use this if your berserker type is extremely heavily armored, but otherwise, it's usually more important not to miss (and get in some damage) than to hit something a little less armored with this. But if it's the difference between causing damage or not, or if you're so skilled you have skill to waste, you might want to get some "free" DR reduction this way.
Other options: If you can't take him in one blow, or you have more than one blow (Rapid Strike, Dual-Weapon Attack, and Extra Attack), you've got a few options. I mentioned one in Eye Shots, above. Another good option - again, in combination with Telegraphic Attack - is to aim for one second-tier target and then one first tier. Limb/Skull or Extremity/Vitals are both good choices. Chop off a foot and then stab his heart, or break an arm so his greataxe is useless and then split his skull.
This holds true if you've got a friend nearby. If there are a few of you and you have local superiority of numbers (bearing in mind how fast a berserker can move using AOA), you can split up the targets - you go leg, say, and your friend hits his skull while he's down. Or you each take a leg and he also gets the skull or vitals.
Now, these aren't your only ways to go. This isn't exhaustive and it leaves off a lot of special "yeah but" kind of cases.
But in general, I find the best way to deal with a berserker is, again, to put him to -5xHP as fast as possible. Barring that, you want to limit the damage he causes. Some players prefer to cripple first and finish off later, but in my experience it's possible to get too cute and end up dealing a death by 1000 cuts and having to cede important sections of the battlefield while you do it. A straight shot to automatic death is better, if you can do it.
And that's how I like to deal with berserkers.