に何が出来る

what can [someone] do

→ に
phrase Uncommon #19,158
what can [someone] do Used to ask or wonder what a person or group is capable of doing. It can be rhetorical, expressing doubt about someone's ability or options. に marks the person or group in question. 出来る is commonly written as できる.
JA: オレに何が出来ると思ってるんだ?
EN: What do you think I can do?

話が大きすぎる僕らに何が出来る

This problem is too big—what can we do?

— ロード・オブ・ザ・リング/二つの塔 (2002)

オレに何が出来ると思ってるんだ

What do you think I can do?

— ブレット・トレイン (2022)