One of the basic tenets of the DC universe is that messing with Batman is... unwise.
Despite having zero superpowers, instead solving all of his problems by throwing money at them until they go away, Batman has earned a spot on the greatest teams of superheroes that the DC universe has to offer, and has therefor thrown his squishy human body at things that one would be forgiven for thinking would be rather unfazed by his efforts. And the punchline is that he keeps winning.
Whether they be superpowered humans, monsters from beyond the stars, or Lovecraftian cosmic entities whose vast power and infinite lifespans should dwarf the Dark Knight's might like an elephant stepping on an ant, Batman has consistently come out on top of them all through his wits, determination, and again - lots and lots of money.
There have been many villains and even heroes that have tried to step to Gotham's greatest son, and none of them have walked away from the experience. Whether from the comics, games, movies or TV shows, these are the most powerful beings that have lost to Batman.
10. The Predator - Batman Vs Predator
The Predator is one of those 80s franchises, like Alien, that gets crossed over with pretty much anything it wants. The Predator is such an interesting antagonist to match wits with, being at once a mindless alien beast and an intelligent tactical hunter, of course there's always the question of who would win in a fight between it and any given character you can think of.
Of course, the Predators made the mistake of coming to Gotham.
This cheesy but fun as hell miniseries saw The Predator go head to head with the Bat-Family, and getting its ass hilariously stomped. From Alfred taking it on with a blunderbuss (which was AMAZING) to Batman eliminating it by beating it into well tenderised hamburger with a baseball bat.
Realising that it was going to become the laughing stock of the Predator hunting lodge due to being beaten by a welfare brat who dresses like a flying rodent armed with a particularly thick stick, the Predator decided instead to commit suicide by stabbing itself to death.
Batman keeps the sword as a souvenir, because of course he did.