A Really Big DealG 50

What the game doesn't tell you is that you also cannot die.

So that's:

Ultra Hard difficulty
Zero deaths
100% kills
100% secrets

The Automap you can collect on each level will show you exactly how many secrets you have to find, and how many kills you need to get.

Obviously, the earlier levels are easier for this, as the secrets can usually all be found without the need for upgrades such as the Double Jump.

Bear in mind that some of the enemies may not spawn until you're almost exiting the level.

I'll update this guide with a level specific walkthrough when I get the time.