Also, OPM is drawn lazily for character, but overly powerful. Just like King is drawn seriously yet he's super weak.
It's the whole Hero theme Saitama fullfills so well to me. He's the hero they need, but not the one they want.
There is a reason that you can abbreviate the show name as OP-man (i.e. overpowered man).
I will admit I think Bleach is just about the only anime which has a unsurvivable attack that remains unsurvivable from start to finish. It just basically never actually hits (I don't think it ever killed anyone important)
IIRC
Shiki Ryougi's hits guided by her eyes in
Kara no Kyoukai are a truly unsurvivable attacks. Stronger or more resistant beings might have less points that she can see to hit, limiting her ability to use the move, (a very few super strong ones can actually reach the point of having no death points for her to attack at all, making her unable to use it), but if she can see a point and actually reach it to pull off the attack then it's guaranteed unsurvivable. Of course the real difficulty comes in the fact that she needs to:
1) Be able to see a point to attack
and
2) Be able to actually strike that point (which in a world of demigods and superhuman vampires is not necessarily an easy thing to do as only a slightly boosted human)

.
That said it's definitely never a case of ever being "she used the move but he resisted it!" type of thing, it's always just either "she got the move off, he died", or "she can't successfully hit him/he doesn't have any points to hit so she can't use the move at all".