Umbreon is fairly easy to KO with Phanpy's Rage attack, which can be set up by Donphan's EQ. On the flip side, unless it's stacked with Special Dark and/ or Expert Belt it does only 10 damage a turn to a Donphan. Depending on what is played with the Umbreon would drastically alter any actual game situations, but it is in no way an autowin by itself.