Not sure if this is a bug or I am missing something in the rules, but when I add Ball & Chain to a character it gives a +1 to the damage multiplier even if they have Mighty.
I also tested this and can confirm. Ball and Chain adds +1 to both Agility and Melee multipliers even if you have Mighty 1+ or Accuracy 1+.
Edit: Actually it looks like a bunch of the Avengers weapons’ damage multipliers stack, even with themselves, so equipping 3 weapons gives you a +3 bonus to the damage multiplier.
Pardon my ignorance on this but how exactly should this work? My reading of the Ball and Chain weapon is that it should add a flat +1 to your damage multiplier bonus for Melee/Agility. It mentions that you can throw it further if you have Mighty so without being super familiar with Marvel’s rules I’d assume it would stack.
Edit: I found the rule that says you use the largest multiplier and they don’t stack.
Edit edit: I seem to have a ticket open for this issue already, it does effect multiple weapons from the Avengers book. I’ll get this report added to that open ticket.