Those might be correct going strictly by the wording of the power but personally I wouldn't allow it if I were judging.

All they need to do is errata the pump to a free action, or to something that cannot be done during another action (but isn't an action itself).

In a world where Spider-Man has better X-ray vision than Superman and Nightcrawler makes everyone wet themselves, Bane's SP isn't THAT dirty.

A simpler approach would be to reword it to "Once per turn, before making an attack roll", etc.

That's probably what will happen.

The down side is that you could not pump him and then make an attack with him during a single MC as you can now.

What was wrong with DrZero's suggestion? That would address the issue and allow the MCed boost.

But what if I'm MCing him to perform an Outwit?

Fringe case, but yeah. I think DrZero's suggestion works out better overall, but the free action idea can work too. MC actions will become using Venom Pump to deal Bane 3 unavoidable damage more than anything else.

During my turn, I use Venom pump for enough to KO Bane. Last action is called. I still have action left. Should Bane be knocked out? I didn't think so, nor did the judge, but my opponent disagreed.

I would think not, since your turn hasn't ended.

Your judge is final on that matter. But since the game ends, so does your turn, so yes I think (and would rule too) that Bane would be KOed after the current - and last, since your judge called for it - action is resolved. After all there is no rules that prevent you from ending your turn without using all your actions during the course of the game, why the end of the game would be any different ?

The end of the turn is as much of a step as the beginning of the turn is. And in this case, that step of the turn hasn't been reached.

How can you end the game and not the turn ?

Because when the judge calls "last action," you don't finish your turn, you finish your action. At that point, the game stops, and nothing further occurs that is outside the resolution of that action. And damage that occurs "at the end of your turn" would not be part of the action's resolution.

Well, I respectfully disagree on that : as far as I'm concerned, calling the last action means resolving the action, then put an end to the turn, then put an end to the game, in that order. And unless an official ruling comes to tell me wrong, I will stick with my interpretation anytime my word will be final. The rest of the time of course I will stick with the local judge way of doing things.

You are correct that in the end it is up to the local judge.

That said, vlad3theimpaler is correct about how it should be ruled when time is called. The game ends after the resolution of the last declared action when time is called. You never reach the the end of turn or round.