Debuff supports get suggested a lot. The case against them tends to be more compelling than the case for them, unfortunately.
Buff and debuffs are equally visible, so that's not a factor.
Buffs make allies feel more awesome.
Debuffs make enemies fell less awesome.
So all things being equal, buffs are just better psychologically.
Now if you're looking for something disruptive, that's a different story. Soraka's silence could be construed as an "anti-magic zone." But a silence is had CC, not a debuff.
We'd be more likely to see something along the lines of. . .
Nameless Piltover Anti-hero, the bane of Camille.
Bio: Piltovian rouge who likes to troll the upper class. Probably out of boredom.
Passive: Pass credit
Nameless' AA's and abilities deal 50% damage to non-minions and apply "Credit" for 5 seconds. Credit is equal to 70% of the damage Nameless would otherwise deal and stacks infinity. Allies that AA a marked target deal bonus damage equal to the credit.
Q: The bird
Send a super bird to follow target ally for 3 seconds, granting them 5-15% damage reduction. The next champion that does damage to the target is dive-bombed, applying a .25/1.5 second stun. Target loses the damage reduction when the bird kamikazes a champion.
W: Nope
Nameless throws a glitter bomb at target location. Enemies caught in the blast are slowed by 10-50% for 3 seconds. Enemies in the center of the blast are silenced and disarmed for 1.5 seconds.
E: Lemonade?
Nameless takes a sip from a tea-cup (WITHOUT EXTENDING THE PINKY!), then throws the rest in target direction. Effect is based on what the tea-cup hits and lasts 3 seconds. Movement is not disabled during the cast time.
Allied champion: +10-30 MS. Doubled when chasing Nameless.
Enemy champion: .25-.5 second root as they wonder what just happened.
Allied minion: +25% damage reduction while they wear it as a hat. Also applies to player minions (Tibbers, Ghouls, crabs, Daisy, etc.)
Enemy Minion: Disarmed for 2 seconds as they drink the Tea Lemonade.
Baron, Elder Dragon, and TT Spider (Name?): .25 second fear. What kind of monster would be brave enough to throw tea-cups at them!?
Nothing: Creates a small area filled with broken porcelain and grounds enemies. Piltovian enemies suffer 1 true damage per second as they realize there was no tea.
R: gg. ez.
Nameless pulls a rocket launcher out of thin air, covers his eyes, and fires it behind him (in target direction). Enemies hit directly are knocked aside. When the rocket reaches max range, it explodes backwards, knocking nearby enemies behind it towards him.
