Umbreon Builds.

[Midnight Umbreon]

Umbreon is my big pokemon. It is my mascot, the only problem, is i don't know which competitive build is best for it. So I'm thinking something like

@Focus sash
252 speed\4def.\252 Sp. Def
Moves: Wish
payback
curse.

Can't decide on a last move...

 

[CrimsonMajestic]

If you are set to run Curse on him/her, you may want to question whether you want to invest Speed EVs onto Umbreon. Also, you seem to lack a Nature; I would suggest Sassy (+SpD; -SpE) Nature, and reinvest your Speed EVs onto HP.

On that note, I am not sure why you are using Focus Sash, since Umbreon has plenty of bulk to withstand attacks to setup Curse(s).

As for your last move, I can think of several options: Protect / Baton Pass / Stored Power / Toxic.

Protect giving you increased recovery viability (not taking damage minus Z-move or Feint), and making Wish a bit more viable.

Baton Pass if you desire passing your Curse boosts onto another 'mon.

Stored Power (Psychic-type; Special-based; 20 base power) will increase damage with each boost (+20 per individual positive stat boost; cannot be lowered via negative stat changes). This will also give you some increased offensive coverage, if you desire.

Toxic could also be used to whittle your opponent's mons down (particularly those with high HP and/or defenses).

 

[Midnight Umbreon]

Cool thanks! So I could use one of two things for the items...
Lum berry
Leftovers.
And then I suppose I will give it toxic

 

[Dragon]

Baton Pass if you desire passing your Curse boosts onto another 'mon.

Baton Pass is banned from competitive play, though. I would personally recommend a set like this:

@Leftovers
~ Wish
~ Protect
~ Toxic
~ Foul Play

Wish + Protect is a good combination with Toxic, healing yourself while witting the opponent down, and Foul Play punishes high attack pokemon. If you're using Curse, I recommend:

@Leftovers
~ Curse
~ Payback / Foul Play
~ Wish
~ Protect

Sort of the same concept, but this set lacks Heal bell, so, you'd have to rely on a cleric on your team. I hope this helps you; good luck. ^^

 

[CrimsonMajestic]

You could also consider the so-called confusion berries that restore 1/2 max HP when down to >~1/4 max HP. The berries are:

Aguav Berry (causes confusion to Lax, Naive, Naughty, and Rash Natures)
Figy Berry (causes confusion to Bold, Calm, Modest, and Timid Natures)
Iapapa Berry (causes confusion to Gentle, Hasty, Lonely, and Mild Natures)
Mago Berry (causes confusion to Brave, Quiet, Relaxed, and Sassy Natures)
Wiki Berry (causes confusion to Adamant, Careful, Impish, and Jolly Natures)

Baton Pass is banned from competitive play, though.

That is assuming we're talking Smogon rules, and/or any ruleset that has adapted their rules. If so, fair enough.

 

[5qwerty]

As CrimsonMajestic said above, Focus Sash and 252+ Speed are not good for Umbreon. I would go for Leftovers for the item, and 252HP/252SpDef/4Def with a Careful Nature for the EVs and Nature.

For the last move, Heal Bell or Refresh are good moves because you can get worn down by Toxic when trying to set up. I would also consider swapping Wish for Moonlight, but that's up to you. Moonlight has less PP, but Wish comes in on the turn after.

EDIT: Ok I didn't refresh the page and didn't see Dragon's post. One thing I would like to add is that Foul Play uses your opponent's Attack stat (including their stat changes) and your own items, Abilities, or statuses, so Curse Foul Play doesn't really do anything.

 

[Midnight Umbreon]

Oh gosh, I said speed? Fllbrrt I meant HP lol. Anyway so here is the plan

Umbreon
@Leftovers
ccareful
HP252\Sp.def.252\Def.4
wish
protect
curse
Payback
Or with a persim berry to avoid poison

Mostly my only problem with this is that I watched a Verlisify video w here there was an In brain built like this

 

[PlatinumDude]

Oh gosh, I said speed? Fllbrrt I meant HP lol. Anyway so here is the plan

Umbreon
@Leftovers
ccareful
HP252\Sp.def.252\Def.4
wish
protect
curse
Payback
Or with a persim berry to avoid poison

Mostly my only problem with this is that I watched a Verlisify video w here there was an In brain built like this

Verlisify is generally looked down on because he comes up with suboptimal sets.

Umbreon's pitiful Attack means that Payback will inflict pathetic damage even with the damage bonus. It's better off using Foul Play to circumvent this as well as use Heal Bell in the last slot to cure status problems for itself and/or teammates.