I just completed the Phi Infinity Trials. Unlocking Spider-Man's symbiote was the hardest for me because I'm not comfortable playing as Thanos for his solo trial. In case it helps anyone, here is the setup I used to three-star the challenge:
Thanos at level 100
2 Each Red ISO-8: Gives 3.4% HP recovery every 10.0 seconds
2 Each Orange ISO-8: Increases ability damage by 20.2%
Strategy: Incineration Beam all day, every day, from a distance. Use Thane's portals against him to avoid the confusion attack or use Ultimate Power to dodge. If you stay too close to him in the first half of the fight, Thane will attempt to trap you in a cube.