Why is it that Starlight (The Boys character) can punch through bricks but criminals have to be hit several times to incapacitate them?

It's been a few months since I saw it, so I'm not 100% certain of the portrayal, but if you think about the super strength trope, there's no way a person with super-strength would be punching a normal person as hard as they could.  It would be instant death.  So you would want to punch a BIT harder than a normal human punch, but not DRAMATICALLY so.  And guaging that would be hard, so you'd probably err on the softer side.  Which means you may not get a one hit KO everytime, but it probably doesn't take too many to produce the effect.

BTW, if we're applying real world logic, a KO punch isn't 'no big deal' like Hollywood portrays it.  That's a severe concussion and possibly long term additive damage.  I'm not saying it's wrong, but it's not something that should be taken as harmless as Hollywood typically portrays it.