Wolverine's idea of revenge is a living nightmare. Wolverine may be a member of the X-Men, but he has always been willing to cross lines his teammates would never go near. He's even willing to kill - which is one reason Logan has often wound up leading black ops teams.
That means you cross Wolverine at your peril - a lesson many villains have learned the hard way. That was perfectly demonstrated by Matsu'o Tsurayaba, a high-ranking member of the Hand who played a major role in the death of Wolverine's one true love, Mariko Yashida. Wolverine swore a vow to make Matsu'o pay - and it was one he more than fulfilled.
Wolverine promised to return to Matsu'o every year, on the anniversary of Mariko's death. Every year, he would use his Adamantium claws to cut off another part of Matsu'o's body. Matsu'o initially took this to be the exaggerated oath of a grieving man, but he learned otherwise on the first anniversary when Wolverine tore through Matsu'o's bodyguards and cut off one of his arms. The next year, Matsu'o hired an army of Hand ninjas to protect him - and Wolverine tore through them, before cutting off an ear. Matsu'o's life became what he called a "wretched existence," as every year he lost another part of his body - his nose, his gall-bladder, whatever took his fancy at a given moment. "Every drop of blood is payment for what he took from me," Wolverine swore, "and it'll never be enough."
Here is the irony: in his bloodlust and rage, Wolverine was being the exact opposite of the man Mariko believed him to be. She refused to believe Logan was an animal or a monster, and instead looked deeper, seeing the man who fought against his animal instincts and against his berzerker fury. No doubt Wolverine knew this, in his heart of hearts, and he directed the self-loathing that bubbled up within him against Matsu'o. Every time Wolverine cut Matsu'o, he was slashing at his own soul.
It all came to a head in the Psylocke miniseries, when Matsu'o engineered his own suicide by the superhero. He deliberately angered different metahumans - a pyrokinetic named Jinn, and of course the X-Men's Psylocke - and manipulated them into seeking his death. Wolverine intervened, furious, and he and Psylocke fought to a standstill - as he came close to killing her. But, in the end, Logan relented and allowed Psylocke to put Matsu'o out of his misery once and for all.