I thought “maybe he’s not that evil” but
- He could’ve pick him up once he was done
- He decided to involve more Maulers instead to beat him up and stop him
I get it seems like a plot hole, but I’m gonna play devil’s advocate…
So during this time Angstrom was understandably under A LOT of mental strain. He didn’t expect anyone to show up, no less someone who The Mauler Twins would have great difficulty dealing with.
Therefore, as it’s an extremely high pressure, high risk situation, he defaulted and remembered all the other Mauler Twins he had stashed in this very room, and brought them into the fray.
Yes, he could’ve opened a portal for Invincible, but that also includes Invincible actually going through the portal. From what we’ve saw so far he can’t open a portal on someone, and since Invincible was comfortably dealing with the single pair of Mauler Twins, he could’ve easily avoided said portal.
Because that would be a different story than the one the creators wanted to tell