Kayle, Yorick, Nid, Jayce, Panth
All 5 really stick it to Garen.
Kayle is by far the absolute hugest screw you to Garen as her kit is perfect for screwing him over.
You can kite him all day, shut down his passive by simply attacking things near him and splashing him.
The trick is to use heal to out run him until he uses Q to catch up, and then as soon as he uses his Q, hit him with yours. He can't even touch you doing that.
Then when he gets low enough to kill him, bait him in and ult yourself when he would want to ult you and kill him from within your ult...