This is the only Umbreon I use:
Umbreon (M) @ Leftovers Trait: Synchronize
EVs: 252 HP / 124 Def / 56 SAtk / 76 SDef
Bold Nature (+Def, -Atk)
Traps Gengar, checks Snorlax. Not terribly good at either. Umbreon is hard to kill if played well, but doesn't really have too much of an impact in most games.
Also, fuk Chaosbreon.