I've been GMing GURPS for a long time. I've heard a lot of complaints about enemy abilities.
I joke that the only time players consider an attack fair is when:
- the enemy has to roll "to hit."
- if the attack hits, the PC can roll an Active Defense of their choice.
- if the defense fails, the PC should get a resistance roll, with all applicable bonuses and some marginal bonuses. Success should completely negate all effects. Critical success should carrying immunity to further attacks!
- if the resistance roll fails, immunity should apply broadly.
- if immunity doesn't cover it, DR should apply. Preferably the heaviest DR possible.
- damage shouldn't have any special effects due to hit location other than typical injury modifiers.
- damage that results shouldn't be any harder to heal than other attacks.
Attacks that are missing some of those are cheap. For example:
- automatic hits are cheap. They bypass the essential fairness of forcing "to hit" penalties via movement, Blur, being SM -1 or lower, etc.
- Reducing the choice of defenses makes it cheap. Not being able to have their character predict what defense would work is also cheap. PCs should be able to eyeball any attack and understand the fundamental nature of its susceptibility to being Parried or Blocked.
- Penalized resistance rolls are cheap; lack of resistance rolls is very cheap. Damage that results even when you succeed is as cheap as cheap can be,
- Failure should inflict a small, flat effect but not be determined by Margin of Failure. That's cheap, too.
- attacks which reduce DR are fair, but not especially so. Ones that bypass DR are cheap.
- special damage effects, like scarring, blindness, stunning, etc. are cheap. Especially if they follow-up despite DR.
- attacks which are hard to heal or resist magical healing are cheap.
I say I joke, but there is a lot of truth, here. Players get used to defenses, resistance rolls, immunity, and the ability to heal damage relatively easily in most games featuring supernatural effects. Once you get used to that, it seems . . . unfair when some damage just gets right on by. Or no matter how hard you've made it to hit you it seems crazy that some attacks just hit, especially if they have some kind of appearance that matches something with a "to hit" roll - eye beams? That's just a laser, you need to roll "to hit" with lasers, right? Therefore . . .
And so on.
Me, I lost all sympathy for this a long time ago. The more powerful the PCs, the more willing I am to dump out "cheap" attacks and "cheap" damage. Since players in GURPS seem to love to maximize defenses so as to have a 16+ to defend against almost every possible attack no matter how many come, plus Luck and Bless to negate criticals, it's important to be able to deploy automatic damage and "cheap" effects. They actually serve to provide a challenge more often than 1 in 36 times . . . and then only if you get that multiple times per PC per fight.
Don't apologize for your auto-hit armor-bypassing no-resistance attack. It's part of the game.