So thanos' trait reads
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.

And ravager's reads
I CAN EARN THEIR TRUST: Ravager and adjacent friendly characters can't be placed by the game effects of opposing characters.

So if I put my 2 highest point characters next to ravager, can thanos not use his trait at all or can thanos just use his trait for the next 2 highest point characters?

If Ravager, and/or adjacent friendly characters, are the two highest point value opposing characters, Thanos' power is "trumped" and he cannot place them. His power doesn't say he can place the third, et al, highest point characters. So it will do nothing.

My question is: if he tried, would Thanos receive a power action/token and fail - OR would he not be allowed to be given the action in the first place?

He would not be allowed to be given the action in the first place.

Ok cool thank you

And actually, you just need to make one of the two highest-point figures an invalid choice in order to stymie Thanos. What I mean is, you just need Ravager next to one of your two highest point figures, freeing up your other highest point figure to do whatever it wants (such as advance on Thanos).

If Thanos can't summon both of the two highest point figures, he can't summon anybody.

Just wanted to add the if you have 2 figures that are the same points example 150 he could still place them however with 3 figures at same cost exmaple 150 he can t correct this is if someone is not playing Ravager.

I you have 3 figures that are all 150 points, Thanos simply picks the two highest point characters and teleports them (2 of the 3 figures that are 150, as chosen by Thanos' controller.

Just wanted to add the if you have 2 figures that are the same points example 150 he could still place them however with 3 figures at same cost exmaple 150 he can t place them. is this correct if someone is not playing Ravager.

Oh I thought they ruled he wasn t chosing it just was the 2 highest point Figures and since there was a 3 way tie he couldn t place becasue it does not say choose.

Nope, he chooses the 2 highest point characters. So if it's tied, his controller picks.

Great to know thank you ;')