Star Wars: The Force Unleashed

Easily done on TIE Fighter Factory, right in the first corridor. There, you'll find 3 gonk power droids and 2 astromech droids. Kill them, save your game, then select the same level on the 'Mission Select' screen from the pause menu. You'll be able to 'Load Last Save Point'. This'll respawn the 5 droids. Just do it 6 more times and *ding*, achievement.

This is easily done if you have the Jedi Temple Mission Pack. If you do not have the map pack you can follow Andreka0's solution. He has a good solution but I think that this is easier in the long run.

After you enter the temple you will need to fight a group of Shadow Troopers and Jetpack Troopers. After you clear that group use force grip to raise the door on the right. You will follow a corridor and come to the Padawan training room. Combat droids will continually spawn and attack you until you destroy all eight statues, which act as spawn points.

Destroy 35 droids here and the achievement will unlock.

Can be done easily on the first level as the Apprentice. You'll find loads of droids at the begging so just have fun slicing and dicing them. Keep an eye out for the smaller droids and keep breaking them.