This is my solution to earning the Brave One achievement.
To earn this achievement, the game asks you to have your hero max out his level to 31, while the friendship needs to be maxed out at level 21. By the time you are done with your initial playthrough, you won't earn this achievement. It is possible, however, to grind before meeting up with the final boss.
First, let's begin with preparations, shall we?
-First of all, you will need to find every fruit and treasure in the game, including the fruits that enhance his elemental powers. There are three fruits to find for each power, four powers in total. If you are having trouble finding either the fruits or the treasures, please use the link below to find the ones you are missing. http://www.xbox360achievements.org/forum/showthread.php?t=28...
-If you have followed the entire guide from the link I presented above, you should have every piece of clothing in the game. If you do, that means you have all the matching sets for each of them. You will need to find all the pieces for the Bandit outfit and have them equipped. They will give you extra Life and Friendship shards for each kill that you perform. You will need it.
-Once you earned every treasure chest and fruit in the game (you don't necessarily need memory shards, unless you are a collector and wish to earn those), you need to make your way to Arkela Castle and find/fight your way to Arkela Castle - Hall and Arkela Castle - Main Tower. You will need to clear out the enemies in both rooms when you first go through them. Otherwise, this will not work. Once that is accomplished, make another save.
Now that preparations are complete, this is what you will need to do.
-Arkela Castle - Hall has seven enemies, with the Main Tower having six enemies on the left side of the room where the four fountains used to be. With that in mind, for the Hall, target the enemy that's either on the left or the right side that's nearby the foot of the staircase. For the Main Tower, target the one in the middle. Make sure, for either room, that you stay out of sight while attempting to target. Once you have found your target, go ahead and command the Majin to use Purification. If done correctly, he will go on ahead and the enemies will spot him. He will use Purification, crystalizing them.
-You need to have at least up to four or five enemies become crystals for this work. Once that's done, DO NOT get onto either side of the Majin. If he does so, he will grab you and twirl you around, making you less successful. You need to be in front of him as you hit B, so that you can start striking the crystals, one at a time. If done right, get to another crystal nearby and hit B again. Tepeu will strike that crystal and from there, when you are nearby another crystal, hit B one more time (this is when the bar is full). If done right, both the hero and the Majin will unleash their finishing move, destroying all the enemies in that room. A lot of life and friendship shards should appear.
-You will need to go back and forth to each room to earn these kills. Once they are gone, immediately head to the nearest save point, pretend like you are switching out your costume, then immediately back out. All the enemies that you've killed will respawn, allowing you to repeat the described method above as much as you want. If you need more magic power, I recommend heading to Arkela Castle - Courtyard and starting a fight with the shielded soldiers, hitting them as quick as possible to regain all three magic bars. If you killed one and the other is stunned, have the Majin wait until you alone attack with your weapon until all the bars are filled, then go ahead and kill him as well.
If you follow the preparations I've laid out for you and do this correctly, you really won't have much to worry about. It is really all about grinding and it's very time-consuming, especially the friendship shards. If you have the Bandit outfit pieces all equipped, it should go a little faster. I found that if you clear the Main Tower room twice (you will need to respawn the second time), then the Hall area once, you will gain at least 3000 friendship shards at once. Then you will have to earn your magic power back and doing it all over again.
This is what I used and it helped me a lot. To see what you need to do, check out the video I included in this solution of mine. All credit goes to Achievaholics for creating and posting this video for everyone to see.
I hope my solution guide for this achievement helped out greatly and if given a negative vote, please tell me why and I will amend it as best as I can. Have fun and good luck!