Could it be:
Imagination
I am the initiator of this riddle
You used your imagination to make this riddle
I am the beginning of everything
Everything that is created starts with someone's imagination (inventions, etc.)
I am the origin of god
The idea of god came from people's imagination
But not long ago god was the origin of me
God created people with imaginations
In some way I am god
Same idea as "origin of god"
And even god is stranded without me
Same idea as "origin of god"
I live even if you kill my body
Really not sure with this
you can kill me! But never be sure I don't come back
You can stop someone's imagination temporarily but they could still be imaginative later
I can be the greatest thing in your life
Being very imaginative can be great for your life.
Or destroy everything you love
Imagination can cause denial/hallucinations which ruin your life.
You will need me to find the answer
You need your imagination to find the answer