This is a pretty straight forward but difficult achievement. The requirements to get 110% are:
1) Complete the level on Paladin Difficulty (Including DLC)
2) Complete the Trial for the level
3) Collect all Upgrades and Gems on that level
I have created guides to assist on the Trials for each chapter, I will be creating one with tips for Paladin Difficulty and Another user has created guides on the Gems. I recommend checking those guides out.