Mr. Green
Super Freak
I was going to guess the only way to kill him was to cut off his dome!
Dome as in his skull? If so, I am still not sure if it will work. He will lose his memory for sure but he will regenerate parts of his brain back? If you believe in Ultimate Wolverine vs Hulk, Wolvie's head was cut off by shield and this was after he was nuked at ground zero. Or at least a big, big bomb was droped on them both. He even survive with no oxygen, he simply hybernate.