New Death Passive: If a nearby ally dies, you lose your sh*t
Garen's new mechanic is pretty neat, and definitely a unique reason to bring him into a game. I think there's still some room for expanding on this idea on another champion, maybe a new one.
"Champion wigs out and goes nuts if an ally dies nearby them, gaining some sort of boost or effect temporarily"
Garen is a man of justice. His passive is a call to action rather than an emotional reaction. It's also global and "full time".
This new one would be more local to whatever is going on in the champion's immediate vicinity, would be more momentous and immediately impactful. This champion could be played to bolster team-fights and pressure the enemy team into looking for isolated picks instead.
Also let's think about the immersion and hype a player will have with this mechanic, in a team game. You killed my carry, prepare to die!
P.S. where is the Mundo rework?
P.S.S this is not supposed to be on Garen, I mean another champion