First time, went in blindly with my AER farm team (non-lvl100 Sekus, Diva and 9s, lvl 1 arks ofc), then picked up support 2b with beast hunter. Boy, curbstomped for sure.

Second try, I went more serious with lvl 100 units this time (A2, Drei, and SGorm) then STheria supp. I thought I'll have more chance winning, then I got really confused those enemies were hitting me back to back when they're supposed to have died or at very low hp, like damn. A few moments later, yeah they're immortal and hitting back 10x harder, it's very painful and humiliating to watch, and the healer can't catch up at all.

Third try, I said fck it, eat this uber thicc friend Lougseus, and the rest is history. Although same as you op, I got no clue how will I get that no ded achievement in the future.