Random Most Glaring Unexplained Plot Holes In Marvel Movies (14 items)

(#10) How Does Howard Stark Obtain Vibranium In The First Place?

Howard Stark creates an indestructible shield made of vibranium, but never explains how he got it. Where did he find the rare material? Did he visit Wakanda? Did he get it on the black market?
(#1) Extremis Can Rebuild The Human Body, But Is Never Used Again

In Iron Man 3, the Extremis solution can regrow limbs and heal human tissue from nearly any injury. So why hasn't Tony looked into that? It saves Pepper Potts, for crying out loud!

Instead of burying it in the archives, why not perfect it and use it to help heal his allies? Surely a man who can synthesize his own elements can perfect this new breakthrough and use it for the good of all mankind.
(#4) Why Does Thanos Give Up The Mind Stone?

So Thanos's big goal is to collect all the Infinity Stones to achieve godlike power, right? But he needs help collecting the Tesseract AKA the Space Stone from Earth. So he gives Loki a powerful scepter that contains one of the stones to retrieve it. Why would Thanos do that?

If he's trying to collect and protect the stones, why would he risk unnecessarily losing one to gain another? In fact, he does lose it! The Mind Stone he gives to Loki ends up embedded in Vision's forehead. So now he has to recover that stone and the Tesseract. For an intergalactic tyrant, he sure isn't that smart.
(#11) When Does Tony Stark's Arc Reactor Become Removable?

In Iron Man, Tony Stark has to keep an arc reactor in his chest to prevent shrapnel from shredding his heart. But in Iron Man 3, he has the reactor surgically removed without any negative consequences or explanation as to why he couldn't do this before.
(#14) Why Is Captain America Entertaining Instead Of Fighting?

So America only has enough super-soldier serum for one guy and what do they do with him? Send him to entertain the troops and ask civilians to buy war bonds.

Steve Rogers might not be the ideal person to be America's best weapon, but his ultrahuman attributes still make him more effective than any regular soldier. Any other private could replace Steve in the USO to entertain (and they'd probably do a better job, too).
(#8) When Does Loki Meet Thanos?

At the end of Thor, Loki is falling through infinite space. He doesn't reappear until The Avengers, when, without explanation, he's hanging out with Thanos. When did these two meet? How did they find each other? How exactly Loki got from point A to point B is never fully explained.