1. Nearly as powerful as Discord and Tirek (Facing BOTH Princesses, making a whole kingdom vanish, growing anti-magic crystals, using mass brainwashing, giving life to a cursed door, making a pocket dimension of nigh-endless stairs, etc.).
2. Maybe the smartest villain (Look at all he did to hide the Crystal Heart! Twilight and Spike got VERY lucky!).
3. Dead serious (No speeches, no arrogance, etc.).