I always wondered if supervillains kept track of each other's plots in case they needed to sabotage or interfere for their own ends. Not like Nazi Red Skull would be on friendly terms with former Jewish internment camp survivor Magneto.
Yes, it was in Acts of Vengeance, where Loki gathered various supervillains and suggested they switch their enemies in a grand alliance to destroy heroes. Loki assumed they're all evil so they'll get along...and then had a surprised pikachu when Magneto used portals, that Loki set between villain bases and their meeting hall, to go to Red Skull's base, wreck it and kidnapp the guy.