Look at how fast the final bosses are defeated with them (and they aren't even at maxed power)...
Note that I'm around an average endgame level here (low 40's). These badges are broken even at much lower levels though, as long as you have multi-hit attacks and a decent number of mushrooms.
As for why I have so many Ultra/Max Mushrooms, the Ultra Mushrooms were farmed with the Game Boy Horror SP (Sworms drop them, and this late in the game the battle should be won instantly with a first strike, so circling around Beanbean Castle while fighting all enemies should give you them very quickly), and the Max Mushrooms were bought right before recording this using the money I collected from the last few areas of the game (and some sold unlimited-quantity enemy-dropped equipment, such as Boos' Random Slacks). (To quickly exit Bowser's Castle, I suicided to Fawful (if you have Swing Bros. Advance, use it to steal a Golden Mushroom first (reset if you get a 1-up Super instead)-- it's the only way to get more than 4, which is also why I didn't save after Fawful) and chose to restart from Beanbean Castle. (Yay for nested parentheses?))
How the Mush Badges work: each normal/Super/Ultra/Max Mushroom you have increases the damage of every hit done by the brother wearing the badge (including Bros. Attacks) by a certain amount, with the exception of attacking an enemy with something they highly resist (Troopeas resist hammer/hand attacks, Glurps resist jump/hammer attacks, Jojora resists everything). It's unaffected by 1-up Mushrooms, 1-up Supers, and Golden Mushrooms.
The damage addition from the Mush Badges also varies between the American and Japanese versions. (Not sure about PAL.)
I apologize to anyone who'd have preferred to read the Fawful text-- I've played this game so many times that the text gets boring for me (and I restarted this recording a few times due to taking too much damage against Cackletta). I know there are other videos of that battle if you are interested in reading the text, anyway.
Despite having played this game so much, though, I almost never succeed at hitting more than once with Knockback Bros. Advance (the problem is that it just doesn't get unlocked on an ordinary playthrough for me). I still attempted it here because it didn't make any significant difference-- Cackletta's heart would have been defeated after two Chopper Bros. attacks even if Luigi never attacked it.
On a random side note, I think Fawful would have been better off with Cackletta's first battle theme instead of Popple's battle theme.
Oh, the game is Mario & Luigi Superstar Saga if you didn't know what the acronym stands for (the game title is in the tags as usual, but not sure how many people check those anymore).
![](https://i.ytimg.com/vi/dWCqc12-VKc/mqdefault.jpg)