Downplayed: The bullying by Evulz causes Bob to lash out in anger and, although his response is relatively mild compared to what it could be, it is equally terrifying to the villain because Bob is normally so mild-mannered.
Although Evulz isn't aware of this, Bob is actually the alter-ego of a superhero with devastatingly effective combat skills.
Bob is very nice, but he also knows a good deal of martial arts. He keeps from using it most of the time because he doesn't feel the need to, but when pushed, he has no problem using very, very painful moves against the subject of his ire.
Bob is usually very nice but becomes a Papa Wolf when his loved ones are threatened.
Bob, a bullying blow-hard, is in fact incapable of fighting for himself if provoked.
Since Bob is not used to practicing violent or ruthless actions, his rage is mostly impotent compared to someone who lives by violence and ruthlessness. His outburst ends up just getting him killed.
Reconstructed: However, sometimes we must lower ourselves to defend ourselves from threats.
Played For Laughs: Bob has zero fighting abilities and looks ridiculous as he goes after his tormentors, putting Evulz on the ground through sheer accident and/or because Evulz is laughing too hard to fight back.
Played For Drama: Bob, trembling, waits until Evulz's back is turned. Bob pulls out a clasp-knife and stabs Evulz until the blade breaks off in the villain's spine.