Adolf Hitler led the Third Reich during World War Two, until he was killed by the original Human Torch. However, Arnim Zola managed to transfer his mind to a cloned body. Hitler kept his survival secret by donning a mask and naming himself Hate-Monger.
When Hate-Monger allied with the Red Skull to create a new Cosmic Cube, the Skull betrayed Hitler by trapping him in the unfinished cube. Hate-Monger's followers, the Kubekut, stole the cube to free him, while the Fuhrer's mind began re-shaping reality into a world where the Nazis won WW2. Captain America and Sharon Carter made an uneasy alliance with the Red Skull to stop it, but Red Skull betrayed Ca and put him inside the cube, where Steve revived his WW2 adventures and would eventually face Hitler, which would result in the end of both. However, Captain America managed to get out of the cube and destroyed it, never sure if it was true what the Red Skull had said about Hitler being alive and inside the cube.