Little bit of a kind of sort of not really bluff from Rob before; Thor having multiple immunities was the big surprise. XD
Also, funny story/probably damning example of how bass-ackwards my approach to this can be sometimes; the idea of Tony being unable to damage Thor under normal circumstances has been in the plans for a long time, mostly because it struck me as a funny consequence of Rob establishing his weapons as "strictly nonmagical".
It wasn't until I started on the Avengers chapter proper and started getting closer to the fight that it hit me... if nothing Tony does can hurt Thor, there was no logical reason for the fight to continue. So I started panicking a bit.
But! I'd also planned for Tony's armor to be able to absorb electrical damage as an upgrade made in response to Whiplash very early in, so from there it was just a matter of connecting the dots together.
Despite all my complains on the previous page, I'm gonna admit: I like your version of this fight MUCH more then in source material.
I hate Thor acting like a dick, striking Tony in the back, striking Steve when he tries to calm him down. And then Steve not throwing his mighty shield at him. And then Thor calming down for no reason. Al of that is so silly!
One of the main advantages of this style of comic is that I can always rely on the good old Pitch Meetings for inspiration when I hit a motivation block.
"Okay so now Iron Man and Thor are going to fight!"
"Why would they do that?"
"Because it happens in the movie and I can't just skip over it."
"Oh okay let's start working on an explanation for that then."
Okay, I used up a lot of my "response" time following up to something from the previous page so...
...I'm just going straight to "the GURPS". The main way one deals with damage in GURPS Fourth Edition is using an Active Defense (Block, Dodge, Parry) to avoid it, or having sufficient Damage Resistance (DR) to safely soak the damage. Normally, DR doesn't do anything more than that but when you have "Powers" in effect, be they ultra tech, magic, psi, super, spirits, divine, infernal, etc. you can get some nice bonus options. Like DR that really does absorb damage.
Absorption is an Enhancement to Damage Resistance in GURPS. Your DR still prevents you from taking damage as per normal, but that damage converts to "points" that can be temporarily spent elsewhere. Even when your "damage battery" is full, your DR still protects you as normal; you just won't be able to "store" that damage. You lose one point per second, with unspent points depleting before spent ones. As a reminder, GURPS combat turns are 1 second long. Though I said "temporarily", there's one permanent way to spent the points: recovery. For every two points of absorbed damage, you can heal one Hit Point. Period; there's no time limit on this healing, and these points never "drain" away. You can still lose those Hit Points by being injured again. Fatigue Points (FP) can similarly be recovered, however it costs three points of absorbed damage per one FP. If this is all you can do with the absorbed damage, Absorption is a +80% Enhancement.
You can also select one of your existing character traits (at character creation) and have your pool "damage battery" points let you temporarily raise that trait. For example, if you want a character who absorbs damage to fuel their Strength (ST) Attribute, then every 10 points of damage can pay for +1 to your ST. So if your Absorption just soaked 21 points of damage, you could "spend" it on +2 ST. At the end of your turn, the 1 unspent point of absorbed damage is lost, but you still have +2 ST. At the end of your next turn, the 20 points of damage fueling your +2 ST drops to just 19. You can no longer afford a full +2 to your ST, but it just convert to +1 ST with the leftover 9 now draining away turn after turn. Again, this version is a +80% Enhancement for your Damage Resistance.
If you can spend the Absorbed damage points on any of your traits, it is worth +100% e.g. it doubles the CP cost of your DR but any trait you already have, the absorbed damage can boost. I think it can also be used to heal HP/FP as well. Getting to the fight from the film, this could be as simple as Tony's suit having the +80% version, only letting him recover HP/FP. How could that be? Another thing GURPS has is "Extra Effort"; you spend more FP doing something, exhausting yourself quickly but you can push your body to its limits in doing so... or in this case, the suit can be pushed to its limits. So the "damage battery" can be tapped to recover FP spent to fuel stronger-than-normal attacks, faster-than-normal movement, etc. Pushing yourself like this can also risk injury... that the slowly depleting points from your "damage battery" can be used to heal, at least if you have need to spend them before they naturally drain away. So, "before" being supercharged, it Tony probably couldn't hit Thor hard enough to do any real damage... but now Tony can push the suit to its absolute limits for a few rounds of combat, hitting hard enough that even Thor feels it.
Author Notes:
Also, funny story/probably damning example of how bass-ackwards my approach to this can be sometimes; the idea of Tony being unable to damage Thor under normal circumstances has been in the plans for a long time, mostly because it struck me as a funny consequence of Rob establishing his weapons as "strictly nonmagical".
It wasn't until I started on the Avengers chapter proper and started getting closer to the fight that it hit me... if nothing Tony does can hurt Thor, there was no logical reason for the fight to continue. So I started panicking a bit.
But! I'd also planned for Tony's armor to be able to absorb electrical damage as an upgrade made in response to Whiplash very early in, so from there it was just a matter of connecting the dots together.