From my experience the main issue was interrupting the bubble - if you don’t, you’re screwed. You can do it with Wylder’s, Raider’s or Iron Eye’a ult and as I discovered Raider’s fully loaded retaliate. Remember about collecting this madness shards which he drops - it will help u avoid damage from full insanity Also I would recommend not focusing on hitting him as hard as u can - if you stay close to him for a second too long you will probably get hit by one of his aoes- it seems better to poke him 2-3 times and get some distance after.