Initially a reply to this comment:
If Mara suffered so much then why Mara still exists? Why didn't Mara
turned down and surrender to Buddha?
There is a necessity for Mara's existence. Hot only seems so hot when you have something to compare it to, in fact if you have nothing to compare it to it is not even "hot", and if the temperature of the comparison point changes, then so may the "hot". There cannot be light without darkness, nor darkness without light. If you do not know evil you cannot know good, if you do not know what is 'bad', how can you ever understand what is 'good'?
We start off with things being in a sense 'bad' so that we have freedom, and this doing us a service, instead of just starting off as angels who can never do any harm, we are tempted and given the choice so that it is not by creation, but by choice that we do 'good' and choose who we are. Another thing is that 'suffering' is really just a creation of the mind, it kind of exists until you are free of it and realise that it is not actually really that real, but really it doesn't exist as such. It's just a concept.
I also think that Mara is going to be a very different kind of being to us so we cannot interpret her in the same way. But she has to exist for balance and freedom.
If you have not helped yourself be free from something you cannot hope to help others. Your power comes from your karma, only when you know how deep the hole goes and how to get out of it can you help others, if you never went down the hole you wouldn't be much use to anyone. Mara is a great teacher. When you see Mara you really see yourself. You have the balance within you and it is your choice.