Game Difficulty for Mass Effect 2 covers information on the different game levels that can be selected by the player at the start of the game. There are Five difficult settings. Once one is selected, you cannot change the difficulty without starting a new game.
After finishing the game on any of the above difficulties, the Hardcore difficulty will be unlocked.
In Mass Effect 2 Insanity is the highest difficulty setting. The only way to unlock Insanity mode, is to complete the game on Hardcore mode without changing the difficulty during the game. Playing on Insanity difficulty with a brand new (level 1) character is very tough as enemies can deal a lot of punishment.
This page indicates the different game difficulties that are available to the game.
Mass Effect 2 Game Difficulty
This difficulty is intended for players who are not experienced with shooters and RPGS or who are more interested in story than combat. Increases the power of Shepard and squad members. Enemies are weaker, have slower reaction times, and use powers less often.
This difficulty is intended for players who are familiar with shooters and RPGs. This is the baseline Mass Effect 2 experience.
This difficulty is intended for players who are experienced with shooters and RPGs and are looking for a challenge. Enemies are tougher, react faster, have upgraded weapons, and use powers more frequently.
This difficulty is intended for players who have already beaten Mass Effect 2 and want a bigger challenge. Enemies are extremely tough, react quickly, have significantly upgraded weapons, and use powers aggressively.
This difficulty is intended for players seeking the ultimate challenge. Enemies are tenacious, react quickly, have heavily upgraded weapons, and use their powers mercilessly. This mode is only recommended for players who have completed the game on Hardcore difficulty.