Yasuo

Yuumi is one of the best support for melee bot lane. There's no positioning issue unlike other supports, mitigates poking from ranged opponents, and turns 6 item + boot late game carry into hyper carry

Katarina

Master Yi

Yi will usually take Hail of Blade, go super aggressive level 1 and cheese enemy

Lucian

Strong early game and your slow interact with his ability

Nilah

Amazing heal and shield interaction, and she goes in like a melee champion (she is melee technically)

Tristana

Good for going all in

Vayne

Yuumi makes up for Vayne's weak early game by improving survivability, and boosts late game

Twitch

Try to level 1 cheese with his invisibility, very high burst

Zeri

Zeri and Yuumi is falling of after the rework

Sivir

Safe farming early, scale hard later

Smolder

Yuumi is not good with adc who can't take sustained fight

Kalista

You'll probably die if she R you out into enemy, but some Kalista player are super good so it varies

Jhin

Your attack speed bonus and on hit heal doesn't do much, he can't increase his attack speed

Ezreal

AP EZ=bad, AD EZ=ok

Ziggs

Yuumi is not good with poking adc

Caitlyn

Her strong early game + your weak early game = weak early game

Senna

Senna is very weak early, and she doesn't have enough mobility to escape

Jinx

Play safe early, scale into teamfight. Very likely to get penta kill

Ashe

You can chain slow with her, but she lack mobility to escape once get hooked

Aphelios

Very strong scaling duo, but extremely vulnerable early

Draven

Draven wants early aggression and snowballing, which Yuumi doesn't have