First of all, Hitler and Stalin are as dead as any other average person on Earth, just rotting below Earth. Them being in Hell is as irrational as saying that Sea isn't salty. They just die, and then poof to non-existence for what we know. That's why there are JAILS for murderers, when you can't really feel their pain in Hell, you might as well feel their pain while rotting in a Jail cell being constantly raped by other inmates.

Plus, there are that say Christians that Hell doesn't exist, and "God" doesn't want you to suffer but will just obliterate you into non-existence. In short words, Hell is just a fairy-tale to scare you shit-less and "repent". There's also the fact that the concept of "Hell" was actually inspired from a Book written by an Author who had a dream about being led through a place where all the sinners suffer. I don't remember it but you can find info about it in the internet.

Second of all, as of visions, nothing really counts as "Visions", it's just Dreams. What we see are the cause of the REM and the high brain activity during our sleep, and at such a time we also face the phenomena called "Dream" (a series of thoughts, images, and sensations occurring in a person's mind during sleep.).
To put bluntly me having a Dream is the same as someone else having a "vision", nobody actually experiences Visions.

And last of all, someone cannot "die" and come back to life, and a near-death experience isn't death, it's literally written in it.

I.e when People drown their Lungs stop (obviously) and so does their Heart stop pumping, and it always depends on that small series of seconds or minutes to define him dead (as he falls unconscious due to oxygen levels and so the heart struggles to pump and eventually stop) or not.

"If no breathing is felt:
What happens when you drown is that you lose oxygen, therefore the best thing to do when someone isn’t breathing is to give 5 big breaths into his/her mouth before doing anything else. Initial CPR guidelines stated that you must provide the person with chest compressions followed by two rescue breaths, however this information has now changed as providing oxygen is crucial. While it may be difficult to get the person breathing (due to water in the lungs) it is important to keep trying to provide the person with oxygen.
If the person begins breathing again check the pulse to ensure the oxygen is moving around the body. To do this place your fingers on their Adam’s apple and move it to the side to feel it beating.

If you can't feel a pulse:
If you can’t feel a pulse then you need to begin CPR immediately, which means giving 30 chest compressions followed by two rescue breaths continuously. This needs to be done repeatedly until the emergency services arrive to take over.
Even if you are not 100% sure if the person has a pulse you should start CPR anyway, as this will pump his/her blood and oxygen around the body for the person.
This is a tiring procedure so you should swap over with someone else to stop yourself from becoming exhausted." - These are instructions clearly clarifying that someone isn't immediately dead as soon as they stop breathing or if they have no pulse.

And to add more to the life after death "theory" -
http://www.dvorak.org/blog/2010/05/30/white-light-when-you-die-actually-...