Is it double Max HP/200 proc? If not, knowing the other stat may help determine where it's best used.
Here are some characters that might be best:
Thanos, Wolverine, Deadpool, Hulk, Weapon Hex, X23, Cull Obsidian, Angel, Apocalypse, Agent Antivenom, Antivenom, Iron Heart, Mantis, Quicksilver, Dr. Strange, Wasp (Nadia)
You could also use it on SW, Jean, Iron Hammer, or Luna... But those characters would benefit more from elemental damage boosts.