Dragon Ball Z Budokai HD Collection

Goku is available from the start. You will need to do Goku's DU at least twice to unlock all the characters you need for the rest of the achievements. Goku's Dragon Universe is by far the longest, so to minimise the times you have to play through it to unlock all characters, make sure you unlock Broly and Omega Shenron on your first playthrough. For Broly, get to the Majin Saga (the last section), and get to the point when Goku is looking for someone to fuse with. Search the southern island chain for a "???", and you will find an SSJ4 capsule. You will need this a bit later. After the scene where Buu absorbs Gohan, search the desert for a "???", and you will see a scene with Hercule. Then head towards the lower red dot, and search for another "???" just north of it. The go back to the dot for a scene with Kabitoshin. Then defeat Buu and you will unlock Broly.

After you defeat Broly, ignore the red dot and go to West City. Here you will get a scene with Bulma. Once you have done this, go to the new red dot and defeat Gotenks. This will open up the fight with Omega Shenron. Defeat him to unlock him.

To save time, before playing this one again, go and finish Vegeta's DU. It is pretty short, so won't take you long.

On your second, after the first battle Raditz, go to grandpa's house to unlock Kid Goku. Then search the mountains in the North to find Raditz' spaceship Enter it, and you will unlock Bardock (you do not need to fight anybody. On this playthough, make sure you skip the steps above to unlock and Broly and Omega Shenron as this will make the final battle with Kid Buu not happen.

The reason to play through Vegeta's DU is so you can unlock Cooler in this one. After your battle with Frieza in Namek, there will be three red dots on your map. Go to the westernmost one (directly below you), and you will fight Super Saiyan Vegeta. Once you defeat him, go to the location in the centre of the map, and fight Cooler. Defeat him to unlock him.

When in the final battle with Kid Buu, hit him with a successful Spirit Bomb attack to unlock Uub. To do this, when you are in your standard form, hit to go into hyper mode, then hit again when you are next to him to start this attack. To make it successful, you need to win the minigame, in which you have to hit when the bar is closer to the top. If you beat Kid Buu in this minigame, the attack will be successful and you will unlock Uub at the end. It is advisable to save before this fight so you do not have to play through to him again should you not get the Spirit Bomb right.