Revenant Trophy

Insane is the hardest difficulty in the game and unless you use a cheat to unlock it instantly as mentioned in Step 1 of the Road Map, you will need to play through the game at least once on another difficulty before it will unlock. There is actually very little difference between Hardcore and Insane so whatever got you through Hardcore, should be enough for this. If you are following the Road Map then after Arrowtree you can call yourself invincible for all intensive purposes as you can heal yourself from anywhere on the map using the second controller.

Though I never advocate cheats, I will point out that the super weapon cuts down every enemy in the game, even bosses, with one shot. If you were to combine this with the fact you can revive yourself an infinite amount of times from anywhere, it naturally makes a mockery of the difficulty but whether you use cheats or not is up to you.