If you only have one opposing player, could I use "teleport my greatest enemy"?

TELEPORT MY GREATEST ENEMIES: Thanos can use Plasticity. Give Thanos a power action and place the two highest point value target opposing characters in squares adjacent to Thanos

I assume you mean character (Thanos doesn't care how many players there are). If so, no. From the Player's Guide:

#049 Thanos
The second sentence of Teleport My Greatest Enemies reads: "Give Thanos a power action and place the two highest point value target opposing characters in squares adjacent to Thanos."

For Teleport My Greatest Enemies, if Thanos can’t target the two highest point value characters, then he can’t use this power.

For Teleport My Greatest Enemies, Thanos must be able to place the targets adjacent to himself. If he can’t, then he can’t use this power.

Well, that's sucks.