Why do you say the dead want revenge?? In most cases i've found them to try and help and guide in the ways of thought from other planes, yes you get angry spirits who clinged to life so much that they refused to move on or be reborn, but they are in the minority, often you can be surrounded by multiple spirits all floating on their plane overlapping ours without even feeling their presence, treat every and all entities with respect and grattitude and you will in general get the same back.
Becasue they dot want to let go of life and are angry over being dead. These sprits can be aggressive but they are just lost and need to come to terms with what has happened. Death is another step in the jounrey not the end of it.
these spirits are angry for many reasons probally they were killed unjustingly and want to stay here others they are frightened to let go of life because they do not no what is ahead of them there are many reasons why there are angry spirits and the normal kind
Every spirit enters the spirit world at some time after death (entrance is called the 'third death') but for some it takes longer to enter the spirit world than others (it can sometimes take hundreds of years, ike the ghost of the Lady Anne at Hampton Court palace) the time just all depends on the circumstances before death, like if you die in quite a painful way it could take a while, but if you die in a peaceful painless way then it's almost a guarantee that you'll enter the spirit realm immediatley. However, most don't know about the 3 death transfers, in fact some people don't even BELIEVE in ghosts. So if they end up as a ghost for quite a while then they'll think that they are condemned to wonder the Earth for eternity, so they eventually end up frustrated and lonely with nothing better to do, so revenge floods their soul and drowns all signs of compassion inside them. Eventually they wish to kill and destroy every last living thing so that people can share in their hatrid and suffering. My dad came across one of them when he lived in America and it said that it would "raise some sort of ghost army and exterminate all of man and animalkind until the world is dominated by ghosts" personally I think that ghost was too deluded with hatrid, but you never know.
The dead want revenge?! Why didn't anyone tell me? I don't think they all carry a grudge. TO the person who posted above me, the people who don't believe in ghosts are most likely atheist but they should realize in a way, science proves it. Energy cannot be created nor destroyed.