A character too strong and played straight would suffer the same faults as a character too weak played straight. With characters like that, creativity is essential. Sure, this character can basically one-shot everyone without trying, but that's the joke, they aren't trying to. The action could be intense, but as a comedy, it's fast paced. I know this character wins, how do you make it entertaining?
Similiarly, if a character is just weak and that's it, then how do you keep me entertained? Cinematic feats of force aren't going to happen, so mix it up. Show off tactics and creativity. Demonstrate this character, who's absolutely pathetic physically, can outsmart even the most capable and seasoned opponents. And not just little tricks, I mean fully thought out plans that can backfire. This is my bias showing, but I'm way more invested in a smart as hell character compared to one with crazy physical strength or magical abilities.
Growth with weak characters are all in their responses and mentality. Mistake they made in the past are corrected (or overcorrected depending on personality). Things that beat them badly before, they account for and have a strategy against. With experience, all of this can become second nature. But ultimately, mistakes are still going to happen, misplays and getting outplayed are common no matter the mental discipline. Growth can be shown like that.