@OP
Don't add your own interpretation of a character's weakness if you want this to be objective or worthwhile at all. Fox's only weakness is not how hard he gets combo'd and gimped. Saying that's it and ignoring everything else is pretty shortsighted.
It's shortsighted on both ends of the spectrum too. "getting comboed" isn't an inherit weakness. If that is the character's "only" "weakness," then Fox would never be comboed in the first place because he'd never get hit because his moves and movement game would always outclass other options.
Characters don't have straightforward weaknesses unless they have a fundamentally polarizing design (Ness, Zelda). Weaknesses come in the form of per-move basises and what moves are more effective than each other in certain situations. That's how characters get hit in the first place, and that's why matchups swing one way or the other. Ness's recovery isn't his weakness, his tiny limbs and awkward stage game are weaknesses.
I went over the concept before on Smashmods I think, but there are weaknesses, and there are weakness "multipliers," or things that end up being abused
as a result of weaknesses.
Strengths/Weaknesses:
How fast a move starts up
Move range (Disjoint)
Move coverage (Relative to the character's hurtbox)
Other priority aspects (Invincible frames, super armor, transcendent priority)
Move safety (End lag mostly, but things like mobility can make moves more safe)
Move damage (regarding shield stun)
Knockback (Regarding beating crouch canceling or not)
Not weaknesses but
are things that get abused
because of weaknesses:
Ease of being comboed
Lightness
Bad recovery
Similarly, Not strengths, but things that capitalize from your strength coming over their weakness:
Move damage (regarding hitting an opponent)
Having combos
Gimp options
Kill options
Think of it as "Does it help me land a hit on my opponent from netural? It's a strength." "Does something beat this move from neutral? That's the move's weakness."