Well, that depends on what "deity" is supposed to mean. If a deity is supposed to be something with contradictory properties or is otherwise defined incoherently or illogically* then that "deity" can't possibly exist.
(*-
Divine Simplicity comes to mind, as do universal possibilist conceptions of omnipotence [those unconstrained by logical possibility])
For instance, a common intuition with monotheist deities is that God exists
a se: to have
aseity is for something to exist unto itself without being dependent** on any other thing outside itself.
(**-Dependency here is probably best understood as this: x is dependent on y iff y's existence is a necessary precondition for x's existence yet x's existence isn't a necessary precondition for y's existence.)
Another common intuition with monotheist deities is that God has absolute
sovereignty: all things are within God's sovereign ability to control so long as it's logically possible to do so.
Most of the time, these intuitions are held together, at which point a paradox called the Aseity-Sovereignty Paradox emerges. It's actually impossible for God to both exist a se
and to have absolute sovereignty; and the problem can be demonstrated in many ways, but it's easiest by putting it in a simple question not unlike Euthyphro's Dilemma:
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If God exists a se and has absolute sovereignty, then that is God's nature to be those things. The question is then, "Did God have any control over its nature?"
1) "Yes" is impossible because in order for God to have sovereignty over anything, God must be God to do so (must have God's nature). This puts the cart before the horse: how could God have had any control over God's nature
without already having God's nature to be able to do so?
2) "No" is impossible given the premises because if God had no control over its nature being what it is, then that immediately implies that
God is dependent on some transcendental thing to God -- whatever that is which makes God have that nature which is beyond God's control.
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Thus it's impossible for God to exist a se and to be absolutely sovereign. One or both of those premises must be wrong by
reductio ad absurdum, and any "deity" which is defined as both existing a se and totally sovereign is impossible to exist.
Does this disprove the existence of ALL deities? No. Just the ones people try to define that way.
There are other examples, such as Euthyphro's Dilemma for deities defined as the source of objective moral facts; or the Problem of Evil for deities with more convoluted groups of properties.