Mind is a measure of a character's resistance to mental stress.

AP Benchmark
1-2 A person can endure the normal stress of daily existence.
3-4 The person's mind is conditioned to withstand stressful conditions similar to those faced by Police Officers, Firemen, and Doctors. Heros with this: Hourman, Rocket Red, Cyborg, Speedy
5-6 The person's mind is equipped to deal with great stress as part of daily life. Undercover agents, leaders of nations, and most heroes fit this category. Heroes with this: Deadman, Green Arrow, Fire, Vixen
7-8 The individual has mental fortitude to continue normal activities even in persistenly painful or stressful situations, such as those experienced by hardened soldiers. Heros with this: Martian Manhunter, Sergeant Rock, Ra's Al Ghul
9-10 The individual will maintain self-discipline and sanity even under strenuous and torture or pain. Heros with this: Wonder Woman, Eclipso, Solomon Grundy, Circe
11-12 This person's mental endurance is at the peak of human fortitude. Heroes with this: Swamp Thing, Raven, Brother Blood
13-15 A person with this level of Mind is accustomed to dealing with alien or inexplicable phenomena, or problems outside of human experience. Individuals can handle the stress equated to "the weight of the world" in stride. Heroes with this: Batman, Demon, Superman, Brainiac
16-18 This person can mentally endure the consistent strain of hostile and taxing conditions such as war for centuries. Heroes with this: Highfather
19-21 As this level, the person has a god-like mental stamina. Heroes with this: Darkseid, Guardians of the Universe, Chemo
22-24 The mind remains whole even in situations where the laws of reality shift.
25-27 The mind can withstand an assult that strikes to the core of the individual's existence. Heroes with this: Phantom Stranger
28-30 An individual with mental stamina at the level of primordial entity. Heroes with this: Monitor, Anit-Monitor, Death, Sandman