I'm stuck on this level, he just won't die. He doesn't even retreat like the dongas.
Any advice?

As u wont have retreat command by now try always moving ahead towards him by pon pon pata pon . Basically dont walk up to him but rather send ur party to attack forward and when he's getting ready to do some move just do chakka chakka pata pon and ur party would move back...or you could just make a mistake and they'd do so . This really isnt necessary though...just get better patapons and maintain fever and he really should be easy . If u maintain fever and keep hitting him he'll flinch which would cancel out whatever attack he might be getting ready to hit you with.

Yep that's it. Maintain fever. By now you might've received the Cedar Wood, if you have save up 900 ka-ching, and use it to make an archer with cedar wood and that red stone...Tytanium ore.
Then you get an amazing archer, and that's exactly how I got past him. Just keep doing the food hunting missions to gather money and make a better army

Ok, guess I'll do loads of hunting missions, thanks guys.

Personally I enjoy building my army. I mean, nothing forces you to do those hunting levels, so when you do them you're exploring levels you haven't explored.
And try disabling your sword guys (Tatepon?). They run forward in hunting and scare animals off. Just let your spears and archers do it alone.

Yeah it's crazy when you have ultra rarepons, Mogyoons and Barsalas. They're a one man army

Thanks, I kept thinking I was going to die in the desert heat and kept using the rain miracle. stupid me, it was easy when I just attacked full on

Do you not have to use it in this? I was using it. You should have to! It does that red thing the desert does when it's burning you, it should tell you if you shouldn't have to.