Marvel's Wolverine is, quite famously, "the best at what he does." What he does, apart from appear on hundreds of covers thanks to his enduring popularity, is survive nearly every attack, thanks to his advanced healing factor that is unequaled in the Marvel Universe. But in Dark Avengers #11, Wolverine's greatest strength becomes his greatest weakness in a shocking defeat for the world's most popular mutant in history.
Wolverine's healing factor is his prime mutant ability, his enhanced senses and bone claws coming in at a close 2nd. His famous adamantium skeleton is not actually a mutation but the result of a prolonged military experiment that only he could survive (anyone without an enhanced healing factor would die horribly during the adamantium bonding process). Wolverine's healing abilities allow him to easily shrug off gunshots, knife wounds, explosions and most poisons. But it can't save him from Molecule Man.
The Molecule Man is one of the most powerful villains the Marvel Universe heroes have ever encountered. With the ability to change and manipulate molecules that make up the observable universe, he is essentially unstoppable when fought with conventional means. In the case of Dark Avengers #11, Molecule Man encounters Wolverine; the mantle is assumed by his son, Daken, but retains the all-important healing factor of his father. "Yes, I had the same problem with your father," Molecule Man admits, discussing how Logan proved problematic to fight. "He always found a way to fight past me." But evidentially, Molecule Man has found a new strategy.
Molecule Man, without seemingly any effort, slowly transforms Daken into a tree, all while Wolverine attempts to fight off the process. It's important to note that his incredible healing factor does not prevent Wolverine from feeling pain, and he's clearly in agony in the above image. Considering Molecule Man's powers allow him to rewrite the universe on a molecular level, it's entirely possible that Wolverine's body is attempting to heal itself as a tree, leading to intense suffering as his greatest mutant ability that has saved his life so many times now works against him.
Wolverine's healing factor is even stronger in alternate universes. In the Ultimate Universe, Wolverine's healing ability is so strong that the mutant can regenerate from a single cell. However in the 616 universe, Wolverine's power, while formidable, is also his staggeringly-painful weakness when weaponized against him.