Venger didn't age, when he was killed, just his body was destroyed (from great damage), but he wasn't truly dead, so he isn't invulnerable (he can suffer damage) but he is immortal because he couldn't be truly killed.

The same thing with Voldemort, he could be damaged but not truly killed, he could lose his body and still be able to come back because of the Horcruxes.

So Voldemort wasn't looking for immortality and invulnerability because just being immortal already brought him forever. And if his body is destroyed, then he could create another or possess someone.

 

Voldemort was immortal and wouldn't die from normal means but he was far from invulnerable.By the threadstarters definition invulnerable would be more like that metal guy from x-men, never being hurt( NOT wolverine).

As long as he could GET hurt he was vulnerable it doesn't matter if he regenerated or not. Relying on something like that has holes, imagine if no one pulled glass out of Peter Petrellis head or so on he would have stayed dead.Besides you are extremely vulnerable while healing, something Harry Potter, Heroes and real life have in common.

 

I'm guessing you're talking about either Juggernaut or Colossus. Juggernaut is (nigh)-invulnerable thanks to the Crimson Gem of Cyttorak. Colossus isn't - he's just really hard to kill. Immortal and (nigh)-invulnerable characters are more common in fiction than truly invulnerable characters (i.e. they can't be harmed at all). The only truly invulnerable characters I can think are also immortal. For instance, (most) gods in fiction, like Living Tribunal in the Marvel Multiverse,

 

I guess, invulnerability and immortality are two halves of a pie. Each one covering for the other's weakness.