You're wrong there.
The Ultimate Kevin arc is canonically OoC for Ben. We've seen that he DOES NOT kill at all during UAF and OV, even when he had the reasons and/or opportunity.
- He didn't want to kill Zomboso, even if he attempted to hurt his family.
- He didn't want Kevin to kill Ragnarok, because he need to "be judged properly."
- One of Plumbers rules is that they are not executioners, but a force of good.
- He didn't allow Ben 23 to kill Azmuth, not only because it was Azmuth, but also cuz "He almost crossed a line with no return."
Even during Ultimate Kevin arc he didn't want to kill Jim until literally the final of the arc, and even then, he wasn't sure about doing it.
Maybe Ben isn't Spider-Man or Batman, but he will walkways try to not kill if there's LITERALLY any other way to defeat the bad guy, and even then, he would try another way.