How Iron Man Would Defeat Every Justice League Member
9. Atom
In the case of the Atom, his core powers involve being able to shrink down in size while still remaining to be extremely strong.
To compare Ray Palmer to any of the characters who Iron Man is already familiar with, the two that immediately jump out from the pages of Marvel Comics are Ant-Man and the Wasp. Utilising this knowledge of his Avengers teammates, Tony Stark one already have one-up on Atom.
Considering Palmer's size-altering abilities come from the white-dwarf star usually attached to his belt, Shellhead could feasibly hack into this and force the Atom to continuously shrink indefinitely until there's nothing left of this Justice Leaguer. On the flip side of this, there isn't all that much Atom could do to Tony as part of his own offense.
Stark has a collection of suits in his arsenal that are made from liquid technology, meaning there aren't even any natural cracks in the armour of these outfits for Atom to get under Tony's 'skin'. In particular, the Bleeding Edge suit literally serves as a second skin for Iron Man.
This is a fight that the Atom simply cannot win. For Tony Stark, it's merely a matter of when not if he'd be successful in beating Palmer.