Hyper
I'm...not sure if you're being serious. Curse Sylveon has already been discussed and its pretty bad. Sylveon's base Atk is terrible and its base Def isn't that great either. This means that you are going to have to boost up quite a bit to do any damage. You also become setup bait for any steel type. You're much better off just using Hyper Voice and CM if you need to boost.
PROS
- Curse actually patches up this mediocre physical bulk
- Return has much more PP than Hyper Voice
- The difference is veeeery little. Don't you trust me? You are better inclined to calcs? Well, then...
0 Atk Pixilate Sylveon Return vs. 252 HP / 0 Def Azumarill: 121-144 (29.9 - 35.6%) -- 31.7% chance to 3HKO
0 SpA Pixilate Sylveon Hyper Voice vs. 252 HP / 0 SpD Azumarill: 123-145 (30.4 - 35.8%) -- 45.3% chance to 3HKO
- Due to Curse boosting Defense, it is easier to set-up than CMind, and is not as easily Revenge Killed.
CONS
- Hyper Voice hits throught Substitute
- Hyper Voice is not influenced by Intimidate
Also, it is pretty bad having Last Resort as a move on a mono attacking, and even Double-Edge.
Anyways, good luck when it boosted up to +3 or more, because if you have not Landorus, Bisharp, or Excadrill, your are royally screwed.