The only way to kill this freaking boss at low lvl without new game +
I recommend farming at least 5 Physical Mirros, can be found in chest from 4F and 3F, I got 6 only farming in 4F, it may took 1h or less if lucky, avoiding fights help too specially at this difficulty.
The fight is pretty easy but a bit of RNG. Contrarian King can cast Rampage (with his broken damage) early in 2nd turn or after he gets a few hits. Always keep a Physical Mirron in main and at least 2+ before he cast Rampage.
Also keep in mind using Rakunda to lower his defense before he cast Rampage while your party has the mirror up.
