How many people here would argue that the biggest threat to Macron in 2022 might be a Philippe candidacy?
As for me, I don't know. It seems to me like the perfect anti-Macron candidate would be a Green who coalesces all the left-of-centre forces and then somehow 1. gets to the runoff 2. gets all the Rassemblement National votes. And well this scenario is pretty absurd.
I think you're close, but actually the perfect anti-Macron candidate is a Green who coalesces enough left-of-centre votes to force Macron into third, then runs the usual anti-FN campaign in the run-off.
Or to put it another way, the perfect anti-Macron candidate is actually two candidates, one ensuring that Macron can't steal the LR vote and another eating into his left flank.