Ermac - Pharaoh

Ermac Pharaoh is the only challenge Ermac character. He has higher stats and better passive than the others as one would expect. His passive is a bit unclear, however, tests show that for each defeated or resurrected character, he reduces the damage by approximately 20% and increase the critical hit chance by about 10-15%. Because of that, he would be best teamed with characters that can resurrect.

When it comes to equipment, he does very well with his signature equipment and possibly a block-breaking one.

Passive

Fear of Souls: Damage Reduction, Critical Chance, Effect Stacking - For every character that is defeated, and for each opponent that resurrects, your team takes less damage and gains increasing critical hit chance. These effects stack.

Specials

Lost Souls - Attack: Medium damage + Stun
Force Port - Attack: High damage + Curse
We Are Many - X-Ray Attack: Extreme damage + Shield

Support

Telekinesis - Bonus Attack in percentage for all Ermac characters
Legion of Souls - Bonus Health for all Ermac characters
Teleportation - Bonus Recovery for all Ermac characters

Equipment

Soul Medallion

10-20% Power generation boost;
[ERMAC] 10-20% Self heal at the end of Special Attack 3 or X-Ray/Fatal Blow attack;
50% Reduced Power cost on Special Attack 2. (Unlocks at fusion level X)

And here is a video review of Ermac - Pharaoh: