pick a character from another moba and pop them into league
Meepo, this guy here has a permaslow dot on his autos, a skillshot root that interrupts channels, and a nuke after a channel time that does damage twice and that teleports him to himself.
His ultimate makes it so he can split into up to 4 characters and each of them farms like the real meepo and has the same abilities but only has shoes for items, as well as sharing stats with the main meepo and if one dies they all die.
It'd be funny even if he'd be terrible without an aghs
Another one I think would be funny to add would be ares from smite, his ult is a delayed pull that hits everyone around him, his q is basically a skillshot that can ground someone for up to 8 seconds and does 105 damage per second base, his fire is % hp damage plus small base in front of him like rumble fire, and his w is basically an aoe tenacity and protection buff.
He'd lose out on his passive since the only aura item in league really is aegis of the legion and what it builds into.