Bugsnax

The legendary bugsnax are the big bosses of this land and they are very adorable but don’t worry, they’d better watch out as you come into their land with the help of your friends.
 
The legendary bugsnax are all locked behind side quests (you’ll see the Mothza Supreme flying around in the wild but won’t be able to draw him down outside of the quest). They are as follows:
 
Mothza Supreme: Unlocked during the “A Slice of Heaven” side quest for Cromdo. This Bugsnak will feature heavy use of the Lunch-pad feature. You’ll need to place a Bombino onto the lunch pad, and aim this at the Mothza to knock it to the ground. When you hit it, it’ll land near a large, ancient pizza slicer. On the bottom of the slicer is a button that you need to use your Snakgrappler on (it’ll have 3 green markings on it). When you do, the slicer will cut into Mothza and it’ll fly back up into the air. After doing this twice, it will start spinning up sandstorms to stop you from hitting it again. For the final hit, you’ll need to fire just before it arrives at its destination so the Bombino flies into Mothza via the sandstorm, knocking him to the ground for the final time. Use the final pizza slicer to deal the final blow and you’ll be able to scoop Mothza off the ground and into your very soul. Don’t forget to also trap a Bombino before you leave so you collect one for Got To Catch Them All .
 
Mama Mewon: Unlocked during the “Throw Down” side quest for Chandlo. You’ll go on an adventure to help him become the strongest Grumpus that ever was! This quest will feature heavy use of the Snak Trap and the Snak Grappler. Your adventure will take you to Flavor Falls where you’ll be in front of a large cave with a large door blocking the entrance. Once Chandlo has opened the heavy door, you’ll then see this big boi in the very centre of the Watermewon Battle Arena. For this boss fight, Mama is gonna shed Wee Mewon’s constantly, however, Mama’s gonna be pissed if you try and take any of them away from her. Around the arena, you’ll see some stone statues. You’ll need to place a Snak Trap in front of these statues, then capture at least one of the Wee Mewons. They’ll be attracted to the trap, so it won’t be too hard. Once it/they has/have been captured, Mama will ram the statue. When she does, she’ll become dazed. Just above her will be a stalactite hanging on the ceiling. Use your Snak Grappler on it to pull it down and hit the Mama Mewon. You’ll need to repeat this 2 more times before Mama splits in half. At this point, Chandlo will join in and distract the Mama while you go in for the kill. He should stand near one of the not-yet-destroyed rocks, but if he doesn’t, just stand next to one and he’ll come over to you. When Mama hits the rock, she’ll become dazed again. Pull the Stalactite above her down to deal the final blow. Pick up the Mama Mewon and feed it to Chandlo to complete the quest. Don’t forget to also trap a Wee Mewon before you leave so you collect one for Got To Catch Them All .
 
Daddy Cakelegs: Unlocked during the “Cake Day” side quest for Snorpy. This will task you with taking down Grumpinati's machinations. This will take part on Frosted Peak, and will feature heavy use of the Trip Shot. When you first arrive at the peak, you will follow Snorpy until you shortly arrive at a suspicious looking pile of snow with a candle poking out, ready to be lit. Using the trip shot and the nearby brazier, you’ll need to light this, revealing the Daddy Cake Legs. Daddy Cake Legs will then run around the arena behind various ice blocks while you try to light the candles on it to wish it a happy birthday. Using the brazier and your trip shot, you need, you can either aim for the Candles (your target line will turn blue once it hits them) on Daddy, or you can attach it to the ice blocks and wait for him to run into the line of flames, which should light the candles. After the first set of candles are lit, Daddy Cake Legs will spawn some Baby Cake Legs that will start leading you to its next location. In this second part, you’ll do the same as before, but this time Daddy Cake Legs will occasionally shoot ice at you which, if it hits you, will put you in an ice block. Mash to get out of it, then continue on lighting the candles. Once they’re lit, he’ll spawn some more Baby Cake Legs which will lead you to the final area. For this final wave, Daddy Cake Legs will be roaming all about. You need to time your Trip Shot line to hit the candles (similar to before but it’ll just be a little bit harder). Once the candles are lit, the birthday party will be over and you’ll be able to grab Daddy Cake Legs. Feed it to Snorpy to complete the quest. this legendary snax will be defeated, and you’ll be able to have your cake and eat it. Don’t forget to also trap a Baby Cake Leg before you leave so you collect one for To Catch Them All .

MegaMaki: Unlocked during the “Dance with the Dragon” side quest for Wiggle. During this side quest, you’ll be using the Trip Shot to knock this flying beastie out of the sky. After a short musical interlude from Wiggle, moving us all to tears, this Bugsnak will spawn out to sea, alongside some tall masts/posts. The aim of this will be to place your Trip Shot onto these posts in the path of this MegaMaki. Once it hits the wire, it will split 10 pieces - 9 MiniMaki and 1 MegaMaki (you can’t grab it yet). You’ll only be able to pick up 3 of the MiniMaki before this rejoins back together (you can pick them up by hand or use the Snak Grappler, the latter of which is recommended since there’s a good chance they’ll be a distance away from each other). Once you have picked up the last MiniMaki, the MegaMaki will then shrink down to size, allowing you to pick this up. Feed this to Wiggle for some much needed musical inspiration. 
 
After completing these 4 side quests, the trophy will then pop. These can be done in any order. If you're having any issues, please reference the video below showing all 4 Legendary Bugsnax in action: