For the Overclocked Achievement the player must "Reach level MAX in Kill Screen". This isn't all that hard, and can be done in conjunction with the Mastermind Achievement.

"Level MAX" is simply Level 10 in the KILL SCREEN minigame. To level up you need experience, which you get from killing monsters. The Monsters in the maze are set to random encounter, so no shortage of opportunity to level up is present.

To get the achievement, simply farm/grind kills in this section of the game, taking care not to kill all 3 Dragons before reaching level 10, as no further XP can be gained from this point forth. You can move backwards and forwards without turning around in a hallway to spawn monsters if you wish. Don't worry about dying while attempting this, as your XP and level progress is kept on death.

If you have any other questions or the phrasing used is at all confusing, leave a comment or message me to let me know. Have fun.