Sabretooth- Wolverine Vol. 2 #10
In WOLVERINE #10, Logan witnesses a bar fight that triggers a memory flashback of his time in Canada. The issue flashes back and forth between present and past time to give the reader a well rounded picture of Wolverine and the way his past has shaped him- that's all well and good. What I want to focus on, though, is the villain Sabretooth and the way he makes himself known in what might be his greatest appearance.
In the flashback scene, Wolverine discovers Silverfox (his girlfriend) dead and drags her body into a local bar. When he arrives, he hears Sabretooth confessing that he attempted to rape her and, when she refused him, murdered her in cold blood. Logan attacks and is overpowered.
Wolverine tries with all of his strength but cannot overcome the older, more polished, methods of Sabretooth. Sabretooth beats Wolverine, smashing him through a wall and beating him with broken bits of wood from the demolished bar, to show his superiority.
This book is significant because it is the first time that Wolverine is really shown as being afraid, as being beaten, and as being totally defeated in battle. As Sabretooth goes to deliver the final blow, by ripping out Wolverine's throat while they're standing on top of a mountain, Wolverine uses all of his strength to push them both over a cliff. The two fall and Wolverine is able to escape but he never forgets, evidenced by this comic book, how badly Sabretooth beat him.