His attack range.
He's susceptible to mental attacks.
He has a huge weakness against magnetic characters.
He's not fire proof: true he can heal even the most horrific burns, but he can't heal if his flesh is completely burned off (Days of Future Past).
He can be drowned.
His joints aren't adamantium so he can be dismembered with a carefully placed blow (see AoA).
Apart from the above listed his main weakness would be...
from a stategic point Vibranium type B (Anti Metal)
For the unenlightened this form of vibranium has been shown to literally shatter adamantium so if one could get this into James's mouth or bloodstream he would literally be ripped apart form the inside out.
Examples of this happening are
1) Alkema's untimly demise at the vibranium arrow of hawkeye
and
2) Avengers #22 where giant man shatters Ultron while pummeleing him with Vibanium.
Wolverine imortal my......
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"In fearful day, in raging night, with strong hearts full, our souls ignite! When all seems lost in the War of Light, look to the stars, for hope burns bright!"
Think of it ... Metal. He's pumped with metal and metal conducts electricty (weakness) and heat (weakness).
I'm sure he has trouble in water from the weight of the metal. And from what I remember, doesn't he had exceptional psychic shielding to help against that kind of attack?
Yeah, you also can't forget the fact of magnetism as a weakness.
I doubt that cutting off his head would work. I remember in one of the comics he was brought down to just his heart and he somehow regenerated by that. It took forever, but it was done ... At least to the knowledge of my friends and I. We could be *completely* wrong.
Wolverine is omnipresent. But that would be an advantage but not humanly possible, but then again he's not human. Wolverine is "hard core." Did anyone read the recent uncanny x-men story about The Hellfire Club returning and Wolverine being injected with a crazy potion that meant he couldn't... fix himself. Didn't work though, he's still everywhere