Consider this a case-study of a DF Knight.
The Knight in my DF game, Vryce, started at 250 points and is now up around 320.
Vryce is ST 17 / DX 14 / IQ 10 / HT 14 / HP 20 / Speed 6.25 (partly bought down as part of his template)
He's got Armor Mastery, Combat Reflexes, Fit, Hard to Kill 1, Hard to Subdue 1*, and High Pain Threshold. He's a Weapon Master (Greatsword.) Oh, and he has Fearlessness 4 on top of this. And Sacrificial Parry, which makes him an effective team player.
His main combat skills are Fast-Draw (Two-handed sword)-16 and Two-Handed Sword-24.
Vryce's attacks do 3d+8 cutting or 1d+7 impaling. This is basically instantly fatal to most fodder types, and nearly so to anything else. Impressive, especially with a 24 skill.
But it's his defenses that make him so dangerous.
Let's take a look at them.
Two-Handed Sword-24 gives him Parry 15 (Skill/2 + 3). He gets +1 for Combat Reflexes, for a 16. Retreat gives a conditional +1, for potentially a 17. Hard to beat a 17, especially since he's likely killing you on his turn, either with 2 attacks or a feint and attack.
Feinting him is hard, you need to beat his 24. A Beat against him is silly, because that increases his roll to 27. Ruses he'll resist with DX-based skill for a 24 again. So it's not likely you'll get him to open up.
Multiple attacks are a good idea, right? Sort of. He's a Weapon Master, which halves multiple parry penalties to -2. He's got a two-handed sword and we're using the relevant rules in GURPS Martial Arts, so his parries drop by only -1 each time.
That means his defenses look like this: 16, 15, 14, 13, 12, 11, etc. before you ever get to his Dodge 9 (he's at Light encumbrance . . . in plate.) With his Reach 1,2 weapon, he spends a lot of time maneuvering to force opponents to close with him, and to keep himself from getting swarmed even as he attacks at reach.
Missile weapons? Good idea. Thrown? Too easily parried.
If there is any sign of real danger of swamping, his wizard ally will usually put Shield on him to give him a defensive bonus. Yeah, almost unfair, right?
Now, you could flank him. He has a greathelm and thus tunnel vision. Fine, flank him and hit away - you've finally struck him. Or maybe you didn't flank him, you just rolled a critical.
He's wearing magical light plate over magical cloth armor (my house rules let magic armor stack) on his torso and mail over cloth elsewhere. Oh, and a greathelm over a mail coif, with a cloth skullcap under that. No penalty for this thanks to Armor Mastery (from DF11). His DR is around 9 on his torso and face, something like 17 on his skull, and 6-7 elsewhere. He's been known to ignore head shots from weaker foes to save his defenses for attacks against his limbs or extremities. He'd be more heavily armored but he really seems to like being at Light encumbrance.
On top of this, his player is basically conservative. He takes risks when he needs to, but not when they aren't necessary. He keeps a spare sword to fast-draw if he drops his main sword, and a lanyard for his main sword if it's a situation where drawing a new one is a bad idea (one sword is magical vs. undead, one isn't). Vryce is overconfident and nearly fearless, but that's reflected mostly in his refusal to back down from a fight and refusal to turn down a risk for riches, not by tossing away the advantages his long-reach weapon gives him. He's no berserker, just a soldier killing as efficiently as he can, sure he'll win if he does just that.
So basically you have this guy who's very hard to hit, armored enough you need to hit him hard, who has extremities that take 6 damage to cripple (so you need double-digit base damage at least), limbs that take 11 (high double digit damage), and rolls against a 16 to stay conscious and 16 to not die. His defenses cover himself and everyone else in a large radius. He's got enough HP that it takes 120 to kill him dead automatically.
In short, this is why Vryce tends to clear rooms of fodder, goes toe-to-toe with trolls and hacks them to burger in seconds, and otherwise deals death without getting cut to pieces.
And he's not even that super-tough as knights go - I'm somewhat equipment-stingy so he's not rolling around in the choicest gear just yet. He could be more destructive, or more defensive. But this is why he's not dead even after a couple of bad fights. This is why he stands alone against tough foes - like last session - and somehow is still alive.
So why did I post this?
Basically I've been thinking about how to challenge my players, and why it's so damn hard to put Vryce in danger. It's pretty simple - the player made a guy tough enough to one-shot most opponents, and then has concentrated on hitting (higher skill, Trademark Move) and on defenses. That's defenses on a broad spectrum - DR, last-ditch rolls to stay conscious, parries, ability to defend the people around him. All sorts of foes have confronted him. Some might even have won, except he wasn't alone or unprepared. Grapplers have been shot up by his scout friends and then hacked down before they get close enough to touch him. Magic has been shrugged off or just taken in return for blows. Crazy monster powers have stopped him cold, but not the whole group. He's been both lucky and good. And so I used him as a model when I made my own knight (Tarjan Telnar, in GURPS Midgaard).
Getting to throw down monsters in front of a PC like this is a large part of why I have so much fun GMing my DF game.
If people like this kind of post, I may look at the other long-lasting PCs in my game and why I think they're still around.
* I know the combo of Fit, HTK and HTS seems odd - why not spend 1 more point for +1 HT? Two reasons - Fit has other benefits, and the others were bought piecemeal, when he wanted a better roll and didn't want to wait until he had 10 points to spare. And I'm not a fan of letting people sell back advantages for higher stats - especially when those advantages do things the stats don't.