Primal Kong Achievement in Primal Survivors

Both of these achievement must be earned in the Cursed Spirits game mode from the main menu, but before you can play it you will need 100,000 Bones to unlock one of the loadout options in this mode. That'll require you to play Primal Spirits mode first to earn that many Bones. Thankfully, the scaling in this game with Bones is absurd. Play a 15-minute Classic mode in Primal Spirits and if you survive to the boss at the 15-minute mark, you will earn over 1,000,000 Bones, which is enough to unlock Cursed Spirits and all the upgrades you could ever need.

Once you've done that, buy a loadout in Cursed Spirits that sounds good and doesn't have a horrible curse. I chose the second loadout because its curse was one less skill to choose from when leveling up, which barely has any impact at all. Other than that, this mode essentially plays the same as the other mode: same enemies, same bosses, same attack patterns, etc., so all the same strategies apply. Focus entirely on DPS. Pick skills that increase attack speed, damage, critical chance, critical damage, add piercing, knockback, etc., and you'll find you mow through all enemies no problem, and can take down bosses ridiculously fast. I don't recommend most elemental skills because you kill enemies too fast for them to take effect. Burning is definitely the most useless. Poison doesn't even slow bosses down, and freeze doesn't freeze bosses, so don't bother with them unless you have no other options. 

As a side note, even though the boss Kong has two health bars, this achievement unlocks aftering depleting the first one, so you don't actually have to beat him.