I'll tell you the most broken (and obnoxious) combo that we've discovered (so I guess you can consider that we'll give this guy these two powers):
Ice Powers combined with any Heightened movement.
So let's go with Ice Powers and Heightened Speed.
For the third power, we can add either Size Change: Larger or Heightened Agility B.
Essentially what we discovered - by having a PC with both super heightened Agility (35ish), lots of movement (maybe a Speed Bonus?) and Ice Powers was that said character could effectively never be vulnerable to conventional, physical damage.
If they move quick enough (and often enough) and have enough movement to spare, then here's how it works.
They move, and dish out a bunch of damage.
Their opponent hits them for a monstrous blast. For argument's sake, let's assume a massive, mega blast that does 50 points of damage!
So said character simply shrugs it off, as they Ice Armor goes from 100 to 50.
On their next move, they use 50" of their movement to bump it back up to 100, then they attack again.
Rinse, later, and repeat.