You don't need any specific champion for the GM fight. But having a reverse-control immune champ is a big help!
I found fighting the Grandmaster is more like playing a game than any other fight. Watch plenty of videos & tutorials and you should be ok. Be sure to have a full stash of revives and potions, and you might not need that many units.
Other than anyone with Reverse Control immunity, anyone can do it. Personally, even with a full team of CGR, Doom, Kitty, Heimdall and Magneto, my r1 Heimdall was the most successful and was the one who took him down. It proves that it's not who you bring, but if you've got enough skill.
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I found fighting the Grandmaster is more like playing a game than any other fight. Watch plenty of videos & tutorials and you should be ok. Be sure to have a full stash of revives and potions, and you might not need that many units.