Question: I have beaten every boss but the moon lord with out potions, but I am wondering if it is even possible to do it. I would like to hear strategies on how to do it.

Answer: 
Yes. There is a process documented online that uses a summoner-focused strategy...

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>  The nurse should be moved to a small room (housing) in an arena, largely cleared of tiles. The player should be equipped with the max (11 segment) [Stardust dragon](https://terraria.gamepedia.com/Stardust_Dragon_Staff) ([via summoning modifiers](https://terraria.gamepedia.com/Summon_weapons#Boost_gear)).  
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>  Enter the nurse's housing after summoning the boss, anchor the player to the ground near enough to the nurse, using a hook.  
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>  When the player's health is low, simply heal with the nurse's pay-to-heal ability.
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>  Provided the nurse survives, this strategy can be repeated several times in succession.  
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>  Note, this is the third point listed in the Tips section of the Stardust Dragon Staff.
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Apologies for the delayed answer. Having successfully utilized this strategy during cooperative play, I can vouch for its effectiveness; the other players were unable to land a single attack before the boss was defeated solely by the summoned minion(s).
I made this little video. I'm beating him without any potions.