It really depends whether or not the Genkidama's power is fully proportional to its ki. Goku said that it was roughly half of what he originally collected when he transferred the ki to Kuririn, yet it failed to kill a Vegeta who was more exhausted than after the fake moon and lost the 10x boost of the Ozaru at that. If it isn't proportional and would have been effective against the monkey, Goku'd need the Kaioken. Otherwise, even Recoom could survive this considering he's quite above 2x an exhausted Saiyan arc vegeta