Nobody Saves the World

This achievement requires you to reach the maximum rank in the Knights Guild, Grandmaster Knight. This is achieved by completing every single side quests given by the members of the Knights Guild. After joining the Guild, you'll be given a handful of quests, and after turning a few in, you'll be able to access more.

Here is a list of all the quests and any tips for completing them:
 

1. Ratsbane - Survive a blow from Ratsbane, the One-Punch Monk. Playing as the Rat, this guy will punch you and kill you instantly. The only way to survive is to level up the Rat Form enough to unlock the Egg. This gives you access to the Hardened perk, which makes it so that a single blow cannot kill you. Once you've progressed in the story past the first Legendary Dungeon and encountered Marty Joe who allows you to combine abilities, you can then equip the Hardened perk on your Rat Form. Talk to the Monk and his punch won't kill you, completing this quest.
2. Gorilla Warfare I - Complete the Ranger Challenge as a Ranger. Head to the objective marker and you'll have to shoot targets with your Ranger Form as they move left and right. Score a 23 to win. For me, there were 25 total targets, so you can only miss two. Nothing fancy here, just be quick with your charged shot to reach the ones in the back.
3. Gorilla Warfare II - Complete the Ultimate Ranger Challenge as a Ranger. Same thing except this one is much harder because sets of 5 targets will come out together in a line, and while it is technically possible to shoot them all with very fast and well-aimed charge shots, it's incredibly difficult to be consistent, and there are five sets of five targets, so even if you manage it a couple times, you'll likely get frustrated trying. Instead, wait until you unlock the Robot Form, and more specifically his Ravager Rocket attack. Equip it on the Ranger and use it each time the groups of five targets come out. The rest of the targets are relatively simple to hit.
4. Save for Last - Find Sir Pumpkin in the Eldritch Gourd Dungeon, and Kill the monsters in the arena without killing the Elite monster: The only difficult thing here is avoiding killing the Elite monster, because it is constantly chasing you and getting in your way when you're trying to kill regular monsters. I recommend avoiding poison because if you accidentally poison the Elite monster, it dies pretty quick. Instead, using the Slug Form to Slow everyone is a great way to keep the Elite monster away while you kill everything else.
5. Dodge This - Find Sir Pumpkin near the Depleted Mines Dungeon, and Raid the Secret Corporation's Power Station and retrieve the Melon Malady:
6. Not Tomb Raider - Find Laura in the Ancestral Forest, and Help Laura in the Animal's Bestiary: Once you find her, you'll go on a separate path and reunite at a chest, with her on the opposite side of a wall. Monsters will attack her, and you need to kill them all from the other side of the wall so she doesn't die. You'll want hard hitting fast ranged attacks. Either the Arrow Flurry from the Ranger, the Tear Burst from the Slug, or the standard shot from the Mermaid are good choices. Equip your highest DPS perks because the monsters will quickly swarm her and likely set her on fire too.
7. The Unbreakable - Find Knight Temporary in the Moletopia Dungeon, and Clear the monsters in the stash without breaking the crystal: the main issue here is that the crystal is destroyed in a single attack, and both enemies AND you can destroy it if you aren't careful. Thankfully there aren't many enemies, but you'll want to use a Form with precision attacks so you don't accidentally hit the crystal. You'll also want to aggro any projectiles that enemies shoot to prevent them from hitting the crystal. Death isn't really any issue here, so just protect the crystal at all costs.

Once you've completed all quests, return to the Knights Guild and speak to the leader. You will then be given a new mission, along with a marker on your map. Head to it to begin an escort mission, and probably the hardest mission in the game.You need to hit lanterns to light the path. If you stay in the dark, you take massive damage. Enemies spawn and try to kill your escort, so you need to protect her, stay out of the dark, and shoot lanterns. This is not easy, as it's really easy for either you or her to die. Thankfully, after four lanterns you shoot, she regens all of her health and pulls out her own lantern for you to follow her. Again kill enemies until you get to the chest. Once you get to the chest you need to fend off around three waves of enemies charging you. Once they're all dead, you're finally done with this mission. All of this must be done in a single run; if you die or she does, you start back at the beginning. My recommendation is to use an ability that spawns Familiars (I used the Magician's), because they can split up and attack many enemies while you use your normal attacks on them too, plus they often end up aggroing for you.

Note: This final mission takes place in the dark cave called 'The Expanse," so be sure to grab The Light Expanse (15G) right after you're done with this mission while you're here.

After you complete that mission, head back to the Knights Guild and talk to the leader to unlock this achievement.