202 – I am playing as Black Panther against Ultron stage II, I have two 1hp drones engaged with me, and I…

Yes, when you reveal Gang-Up, the villain and enemies engaged with you initiate their attacks simultaneously, so you can resolve each attack in any order. Once you start resolving an attack, you must finish all steps of that attack and all abilities triggered by that attack before resolving the next attack.

If Black Panther is engaged with two Drone minions when he reveals Gang-Up, you can follow these steps:

1. Resolve Drone 1’s attack. Resolve Black Panther’s Retaliate 1 at the end of that attack.
2. Resolve Black Panther’s Retaliate 1 at the end of that attack.
3. Resolve Drone 2’s attack. Resolve Black Panther’s Retaliate 1 at the end of that attack.
4. Resolve Black Panther’s Retaliate 1 at the end of that attack.
5. Resolve Ultron’s attack; create the Drone (“Drone 3”) as an Interrupt, then resolve the rest of Ultron’s attack, giving him +1 ATK for having Drone 3 engaged with you. Resolve Black Panther’s Retaliate 1 at the end of that attack.
6. Resolve Black Panther’s Retaliate 1 at the end of that attack.
7. Resolve Drone 3’s attack. Resolve Black Panther’s Retaliate 1 at the end of that attack.
8. Resolve Black Panther’s Retaliate 1 at the end of that attack.

I apologize, the [above] answer is incorrect. There’s a rule that I missed under “Activation” stating that when multiple enemies activate against a player simultaneously, the villain activation resolves first, then the minion activations. This rule should also apply to activations initiated by Gang-Up. Ultron would have to attack first, then Black Panther can resolve the 3 Drone attacks in any order.