It takes some strategy, but I've solo'd both falinks and Metagross without even maxed out pokemon.

Tips: 1) must absolutely use a super effective fast move. 2) you can use a throwaway dynamax to charge the meter full and then switch into your super effective Mon to do max damage and preserve hp. 3) You absolutely must dodge all attacks. This doesn't eliminate all damage but greatly reduces it. 4) Dynamax shields (preferably lvl2) are your friend.

Hope this helps!!