Phoenix force would take this if it was no holds barred. But if it isnt to be included and weapons arent either then id definitely go for Galactus as long as he's well nourished. Thanos knows he's no match for Galactus and without aid can just hold his own from him before having to flee after a while. This was stated and displayed in thanos' recent series about 6 months ago. So top three would be phoenix then galactus then thanos
Nah Living Tribunals second only to the one above all/ Heart of the universe. Followed by the likes of Eternity and the phoenix force. Death holds no power over the phoenix and cant touch it. Death however holds power over galactus who can and has died. Death is always appearing to G askin whether hes ready to giv in to the inevitable. Galactus is indeed a balancing force between eternity and death. He is equal in status to them but not in power
Yeah the force itself cant be destroyed. Its sentient life and pyschic energy of everything in existence including future generations. So unless you can destroy the present and the future forever which you cant then no it cant be destroyed itself. Its avatars physical bodies can be destroyed yet they will be reborn again from a phoenix egg at a different place in the timeline to carry on their work. When jean was recently "killed" by the fake magneto last year in xmen she was reborn many years in the future from a phoenix egg and destroyed the destructive mutant sublime