It's amazing that anyone would ever dismiss Wonder Woman. She's a better fighter than Superman, and more powerful than 99.9% of most other DC characters... and she's got the fight card to prove it. Besides all the villains she's defeated, here are some of the fellow superheroes she's had occasion to trounce.
Let's start big, shall we? In Greg Rucka's The Hiketeia, Wonder Woman swears an oath to protect a woman who also murdered someone in Gotham. As Batman finds out when he goes to capture the criminal, Wonder Woman takes her oaths very seriously, no matter the circumstances. Has there ever been a time where Batman has been more thoroughly defeated when Wonder Woman punches him out of a building, tells him to basically get lost, and then Batman proceeds to immediately run the hell away? I'd contend there is not.
2) Green Lantern
In Justice League #11, Hal Jordan makes the rather chauvinistic mistake or telling Wonder Woman she can't go off to save her friend Steve Trevor (mainly because WW is a bit angry at the time). Wonder Woman does not care for that, so Wonder Woman punches him into a car about a block away. Batman and the rest of the Justice League stop the fight shortly thereafter, before a winner can be definitely named. But given that (as per the image above) WW can break any Lantern construct she wants with sheer force of will, Green Lantern is exceedingly lucky the rest of the Justice League stepped in.
3) The Flash (and Others)
Blinded after a fight with Medusa (where she poured poisonous snake blood into her own eyes to keep from looking at her foe and being turned to stone), the JLA decided to make sure she was still going to be able to perform her duties as a hero. So, in Wonder Woman #212, she has to fight the Flash, Black Canary, Plastic Man and Martian Manhunter all at once. Obviously, the Flash is the big gun here, and Superman and Batman are concerned about her inability to handle his speed… for about half a minute, when WW starts using the change in air pressure to predict the Flash's location. So clearly, Wonder Woman can beat the Flash while blindfolded. It may also be worth mentioning that this fight ends when Superman tries to shoot WW in the back of the head… a bullet that she deflects with her bracelet. While blind.
4) Power Girl
If you don't know Power Girl's origin, the simplest way to put it is that she's essentially Supergirl from an alternate universe (usually). So she's at least part Kryptonian, and has most of their standard powers: super-strength, invulnerability, flight, etc. As far as powers go, Wonder Woman considers Power Girl her equal. And in Wonder Woman #40 and #41 when some bad guys trick PG into an anti-WW rampage, Power Girl literally punches Wonder Woman into Canada. But as soon as she realises she's not going to be able to talk PG down, Wonder Woman reveals the one way Power Girl will never come close to matching her — combat skills.
There has only been one time when Wonder Woman has fully, totally, unequivocally kicked Superman's arse, and that was in the (excellent) Elseworlds comic Injustice. To be fair, though, Superman and WW were at their normal power levels, so keep it in mind. In the real DC universe, whenever Superman and Wonder Woman fight they tend to reach a draw — because they come to a truce so they can team up to defeat actual bad guys, or because one of them is momentarily evil and the other doesn't want to hurt them.
The latter was the case in Wonder Woman #219, where Maxwell Lord tricks Superman into thinking that WW was Doomsday, and has killed Lois Lane. Superman goes all-out — why wouldn't he? — not only punching Wonder Woman into outer space, but punching her back to Earth, too. He blasts her directly in the face with his heat vision. He crushes her wrist in his hands. And not only does Wonder Woman get up every single time, she holds back, because she doesn't want to hurt her friend. She eventually finds a (rather controversial) solution, but the fact is she takes the absolutely worst punishment Superman could dish out, and she's ready for more. Given that she also has a sword of Hephaestus — one of the few items in the galaxy that can make Superman bleed — I know where I'd put my money if Wonder Woman ever decides to go all-out against the Man of Steel.
6) The Entire Justice League
You know how Batman has all those secret files full of elaborate plans of how to defeat every member of the Justice League, in case they turn evil? Well, Wonder Woman managed to do the same thing, in about an afternoon. In A League of One, when she learns of a prophecy of a great dragon that only the Justice League can defeat — but they will die in the battle. Rather than sacrifice her allies, she decides to take them all out, to ensure that she's the only member of the league that will be available to fight the dragon when it arrives. So she'll be the only one who has to die. She captures Martian Manhunter in her golden lasso and teleports him into a terrasphere in a volcano, where he's surrounded by lava. She headbutts Green Lantern and takes his power ring right off his finger. She dropkicks the Flash into unconsciousness. She punches Aquaman into the mouth of legendary mythological monster Charybdis, which it will take him days to escape.
She flat out whups Batman. And when Superman finally figures out what's going on, she tells him that she's sent Batman, Flash and Green Lantern into space capsule, headed straight for the asteroid belt; and while Superman goes to save them, she's going to fight the dragon on her own. She wins and dies — although Superman gets back just in time to give her a bit of super-CPR. Not a bad day's work.