Jessie caught Seviper in A Tail with a Twist after initially being impressed with its sneaky and aggressive demeanor. It had defeated Ash's Treecko earlier in the episode, which is why Jessie wanted it so much. Although Seviper was intelligent, and outsmarted Team Rocket's multiple attempts to ensure its capture, Jessie caught Seviper after it had bitten off a chunk of her hair, mangling poor Seviper with her "Fury Swipes" and "Mega Kick".
Source