through-victory-my-chains-are-tightened
They could Wish all of the squirrels out from Avernus at once. There are less than two hundred of them. But Heaven keeps gating and Wishing in more of them, to replace the ones He takes.
They try to destroy the squirrels more cheaply, to exhaust Heaven's supply. A chain of portals opened through the planes of Hell, from Nessus to Dis, under Time Stop, allows Him to open a well-directed last portal to Avernus and suppress a field-generator long enough for the squirrel to break down.
They still get replaced.
He spends enough power to destroy all the squirrels in Avernus at once, and close all open Gates, and forbid new ones from opening. He tightens the doors of Avernus as far as He can. He is helped by Barbatos, Lord of Avernus and Lord of Portals also; by Dispater, Lord of Prisons, and Mephistopheles, spirit and Lord of Hell itself; Moloch, Lord of War and four more archdevils and a hundred infernal dukes all lend Him their aid.
A barrage of Wishes trying to move in more squirrels batters at Them, tens, hundreds, thousands of them failing, every round that passes inside the time stop.
But Avernus was made to receive new souls from the rest of Creation, and not to be cut off. For every ten thousand Wishes that fail, one goes through. For every squirrel that falls, another takes its place.
They are, also, still Wishing to steal the remaining souls in Coccytus, Caina and Nessus, at a rate that has already exceeded His estimations of the total amount of Wishes Heaven had ready to use. Even if They had found an enormous new supply of diamonds - and They must have, to have or to buy such resources - They would have run out of spells by now.
If the gods are casting those Wishes themselves, after Their earlier fight against Him, they must be exhausted. But that is the best case scenario, and He will not again fail to defend against the worst case.
Do They have more new allies in this war, bringing hundreds of thousands of castings of Wish to Their side? Are they aiming to outlast him, in a conventional war not fought directly by the gods? Will this deluge ever stop?