Rashi #1 and Ramban: With reference to the various decrees and exiles, beginning with Ashur, Bil'am is woefully exclaiming "Who can survive the decree of Ashur" ¹ - who mixed-up all the nations? Followed by ships from Kitim - alias Rome, who will exile Ashur, and who will themselves ultimately be destroyed. ²

Rashi #2 (in Sanhedrin, 106a): It refers to when Hakadosh-Baruch-Hu redeems Himself from Galus and rewards the Tzadikim when the time comes.

Seforno (based on Sanhedrin, 98b): With reference to the coming of Mashi'ach ? it means 'Let him come, but let me not see him!'

Rashbam: With reference to Pasuk 17, it refers to the coming of Mashi'ach, when Hashem carries out His word and he destroys (or subjugates) all the B'nei Sheis.

Targum Onkelos: 'Woe to the Resha'im when Hashem does these things!'

Targum Yonasan: ?Woe to whoever is around when Hashem comes to pay the Tzadikim their just reward and to punish the Resha'im; To break up nations and their kings and to incite one against the other!?

Da'as Zekenim and Hadar Zekenim #1 (in Pasuk 22): It means ?Who can live through what Hashem will place ("mi'Sumo Keil") in the world (Mashi'ach)?!

Hadar Zekenim #2 (in Pasuk 24): After seeing that all the nations will be finished in the days of Mashi'ach, Bil'am lamented 'who will live?'?

Sanhedrin 106a #1 (according to Reish Lakish): ?Woe to the one who tries to keep himself alive through Shum Eil? (by making himself god). ³

Sanhedrin 106a #2 (according to R. Yochanan): ?Woe to the nation that will be subjugating Yisrael when Hashem decides to redeem them. Who will place a coat between a lion and a lioness when they are mating??

Oznayim la'Torah: ?Who can endure all the troubles that Hashem will place ("mi'Sumo Keil") in the world - the suffering caused by Sancheriv when he destroys nations and mixes up the world, and followed by Edom - alias Rome? (in Pasuk 24).