As for Ninjak, he always has been kind of a d-bag. Cocky and arrogant, morally ambiguous but highly efficient. This is the second time we see him disregard what other team members say. The first time, he ignored Harada's plan and that blew up in his face, too. Not a team player. :)
With psionic powers, I would do my best not to abuse them for my own purposes, but everything we do is done based on our past experiences. Intentions and actions are frequently different. That said...
I'd try to save the world from humans. Halt the eradication and man-made mutation of nature. Promote unity with the environment and green living.
I'd want to learn every language in use. Read and understand the text of books (or stories handed down from orators) from every civilization. Gain a world view.
I'd create art, gesturing with my mind. Carve stone, mold clay, paint, photograph that which is hard to reach my normal means. I'd make music, explore rhythm and melodies and what my capabilities could do with it.
I'd moderate negotiations with world leaders, powerful industries,,, helping them to reveal their truths, their motivations, and hopefully, gain some real understanding so better decisions can be made by them and in the future, by the people who elect these representatives.
I'd explore medicine, finding ways to isolate diseases on a molecular level, learn how to excise the bad. Cure cancer. Aids. Autism. Cystic Fibrosis... on and on. Find solutions without drugs. Find ways to communicate with those who can't. Cure comas.
Block mental impulses of sexual predators and domestic abusers.
Ease the mental anguish of victims.
Promote a shared mental empathy between all peoples, religions, political parties... they don't have to agree, but they don't need to be violent in words and actions.
For my enjoyment, I'd fly - untethered, feeling the rush of air around me. Soar, swoop, and hopefully feel free of the weight of the responsibility of power. Hopefully win this contest. Earning a Harbinger Gold would be pretty spectacular, too.
When I finished saving the world through my eyes, I'd find someone to save it from me.