If one interests you, or feels like something the character could do, try to adapt it into a loyalty ability (or even a static!) Dont feel bad if you end up with a classic planeswalker design (5-mana, 4 or 5 starting loyalty, +1 card advantage, -2 to 3 removal, -7 or -8 ult that has the potential to win the game if you can back it up.) This design, and other often seen designs, are classics for a reason: They work
Which do you think will be the best or have the best potential
Vindicate: Description : Vindicate is a sorcery that destroys target permanent
Even the cheapest Krrik deck run away with victories against some very well-tuned decks
Four mana for another 2/2 is underwhelming, but when you cast an instant or sorcery, you make a 2/2 flying Drake token