So the question is why do people seek revenge?
Do you think emotions such as jealousy, anger etc lead to this?

In the article Elite Daily "Why we should leave revenge to karma" Ashley Fern states:

" We think by inflicting similar pain onto this person, we'll make ourselves feel better".

this means that when someone who does wrong to us or makes us feel inferior than them, the person who receives that sort of pain feels a necessity to "get even"
i had asked a question previously about wether or not emotions can lead to revenge and in the article it says
" Seeking revenge does not cancel out the behaviors that hurt you. it just perpetuates the cycle of pain".
this is helps answer my question in a way, because the pain or emotion you feel is what leads you to wanting to get even with the other person

is it true? is revenge really sweet? or is it worth it?

a really good quote describing revenge is " Revenge... is like a rolling stone, which when a man has forced up a hill, will return upon him with a greater violence, and break those bones whose sinews gave in motion"

Revenge never works out in the end, it will either backfire, or will just end up hurting you and maybe even making you feel even worse. it is better to try and make peace with the issue. " the only way to stop revenge is to give it up and accept it"

Romans 12:19

" Do not take revenge, my dear friends, but leave room for God's wrath, for it is written " it is mine to avenge, i will repay" says the Lord

This bible verse basically says that we should not pursue revenge because in the end God will handle it better in a way that you could never handle. There is no need to waste energy on seeking revenge on other people, because it is not our job. there will be a judgement day and God will handle whatever it is he needs to handle.