Solo Machamp Raids

As the raid graph for Machamp shows, the best counters have about 20% total damage output, meaning you will need five good attackers to successfully solo him. This is my experience, too. With two Mewtwos, one Alakazam, and one Exeggcutor you will need at least one more. Machamp Solo Raid Guide lists all options.

Don't need to care about it now because Machamp has ran away due to all the Psychic Types looking for his head.

Mewtwo is a superior counter to Machamp. With 5 of them and a zam, you're all set. Check out https://pokemongo.gamepress.gg/gobattlesim to see if you can defeat it now of if you need to power up some Mewtwos. Or Pokebattler.

Machamp is out of raids atm. So you'll have to wait a bit before claiming your first victory. I dont think Exeggutor is worth using at that low level. If it has good ivs you can level it up of course, it is good filler for that fight.

You can probably solo it. You might have trouble with the harder movesets (DP or double steel), but I have soloed it with lvl 20 Mewtwos and Latios. So if you have 5 Mewtwos you are good.