Life
We all know what the Life Meter is. Every character in Marvel Vs. Capcom 3 has their own Life Meter, and it's an indication of just how much energy you have left before that character is defeated. All three Life Meters are displayed at the top of the screen at the same time, but the Life Meter for the Point Character will be the largest bar and always the topmost of the three Life Meters. Anytime you switch to another active character, their Life Meter will shift to the top and the character who left will swap places with the new active character.
Hit Points
And while it may seem like there isn't much to say more about the Life Meter, there actually is a ton of valuable information you should know about regarding the Life Meters.
The main thing to note is that every character has a set amount of "Hit Points" and this number of Hit Points is different depending on the character. Even though the bars have the same length on screen, the amount of Hit Points in them are actually different between characters. So while it's easy to say things like "X-23 takes more damage than Ryu" or "The Hulk takes less damage than Storm," it's worth noting that this isn't actually true: every character takes the same amount of damage! The only difference is how many hit points they have total, and those with lesser amount of Hit Points just seem like they take more damage. And this is because, as said earlier, the Life Meters are one fixed length visually on screen. So draining half of Trish's Life Meter means she has lost 425,000 Hit Points whereas draining half of Sentinel's Life Meter means he has lost 650,000 Hit Points. But graphically, it will look like the same amount of life.
The average character has 1,000,000 Hit Points. Characters with 1,200,000 are considered characters with high health and characters with 800,000 Hit Points are considered characters with low health.
Refer to this page to see the Hit Point values for your characters: Character Health and Power Comparison
No Damage Scaling
Unlike many other Fighting Games that you may have played before, there is absolutely no Damage Scaling in the Life Meter. No matter how much life you have in your bar, moves that hit you will always do the same amount of damage. So if you have 100% of your health left, 50% of your health left, 25% left, or even 5% left, a move that will do 50,000 damage will do 50,000 damage.
The Magic Pixel
No doubt that, during the course of playing Marvel Vs. Capcom 3, you've noticed that it sometimes feels like it takes forever to finish an opponent off. Even though their Life Meter shows only a pixel of health left, it takes multiple hits to actually finish the opponent off! Some players have begun referring to this as the "Magic Pixel" as it seems like it just has crazy powers to resist defeat!
In actuality, the game was implemented so that the last portion of your health is not represented on the Life Meter. A better way to think of it is this: your Life Meter actually extends into the Timer in the middle of the life bars at the top of the screen but you just can't see it. Instead, whenever your life drops into that section, the Life Meter just leaves one pixel in the Life Meter the entire time until you finally actually become K.O.'ed. So in actuality, it's not one last bit of health that is particularly resistant to being removed, the character actually has more life left than the Life Meter is showing.