Because Hulk is strongest one of all.
Don’t think of it as “unkillable.” I like to describe it like a health bar in a video game. You can damage him and lower that health bar but it constantly refills and it does so very very quickly. You’d have to do a lot of damage in short order to really do him harm and a TON of damage in one blow to kill him. Short of cosmic or mystical damage, nothing else is really going to be a danger to him.
And regarding Abomination in the Incredible Hulk movie and why he can be killed–to steal a quote from Mad Men “It’s not Anne Margaret.”
The effects of gamma radiation on a human being are not uniform. In the comics, there have been several individuals who have been subjected to gamma radiation in efforts to create new hulks. While the end effect is always super-strong and super-tough, the actual results vary quite a bit, and none have turned out quite as powerful as the original. Apparently, the gamma mutation is affected somehow by the physiological (or perhaps psychological) makeup of the person being irradiated.
The Abomination didn’t die. He is still alive at the end
It can’t be that difficult though, as at least two other people have created shields for Cap. When he renounced the Captain America identity, and became the Captain, he got Tony Stark to make him a silvery shield, but ended up giving it back when the two fell out over the Armor Wars. He then got T’Challa to make him a black one, which ended up being used by USAgent. I don’t know what happened to the Stark one.
Yep, it was also shattered by a Gauntlet powered Thanos, and broken by The Serpent (Odin’s older brother) during Fear Itself
The Abomination didn’t die in The Incredible Hulk. He was incapacitated and taken into custody. According t a short subject extra on the Thor Blu-ray, The Counsel wanted to recruit him into the Avengers.
Also, The Abomination starts off stronger than The Hulk, but (unlike The Hulk) he doesn’t get any more powerful as he gets madder.
“The madder Hulk gets, the stronger Hulk gets.”
Wakandan vibranium. I meant to specify that.
Those substitute shields were made of materials inferior to the original, either steel, pure adamantium, or pure Wakandan vibranium. The original shield alloy has never been duplicated through conventional means.
IIRC when Cap receives the silver shield, he comments on just how close to the original it is, so I don’t think it could be described as inferior
No, it has been damaged, one time by none other than Thor himself. He was in his “King Thor” persona, and he possessed the Odin-Force, in addition to all his regular powers. He struck the shield with Mjolnir, and damaged it. Later on, when Cap and Thor had patched up their differences, Thor repaired the shield, again using the Odin-Force.
The issue was :
Avengers Vol. 3 #63 (March 2003)
Wait, so Abomination is alive? He can’t turn back human, right? So how are they keeping him contained? Will he show up again?
Man, people really liked this movie…
Grrr. Puny Internet thread!
How about on flowers?: The Effect of Gamma Rays on Man-in-the-Moon Marigolds (film) - Wikipedia
Marigolds strongest flower there is!
Just remember the first rule of thumb to survival in a Champions campaign: If you don’t have the body, it’s not dead.
Yes, The Abomination is still alive.
No, he’s stuck that way. I have no idea how their holding him in the Movie-verse. In the comics, he would have been held in The Vault, but it appears to have been destroyed.
If The Incredible Hulk gets a sequel, I’m sure we will, probably as a minion of The Leader.
Not necessarily true for Mechanon. 
That’s even worse. Momentum is a vector, not a scalar like energy: It can’t be reflected. If a projectile bounces off of a barrier, it’s transferred momentum to the barrier. If the barrier is massive enough, this transferred momentum might not be noticeable, but that would take something far more massive than Cap’s shield.
Isn’t that the guy on Jersey Shore?