Æon Flux came out for the PlayStation 2 just like Oni, but four years later, so one can expect some sophistication that wasn't possible for Oni. For instance Æon Flux looks better graphically and uses ragdolls for KOed enemies. However, Oni's melee combat and gunplay is more interesting and you have more direct control over the moves that Konoko performs. Oni's animations are also better, though Æon Flux's do have plenty of character, inspired by the original animated property. Where Æon Flux really shines in comparison to Oni is overall mobility. That being said, not all of the features you see on this page would have suited the more realistic and slower-paced physics of Oni.
Here's how Aeon handles small increases in floor height.
Aeon handles mid-height obstacles such as this one like hurdles.
With a button press at the right time, Aeon can also vault off hurdles.
Jumps that rebound off walls are possible, as well as wall-to-wall jumps.
Aeon can run up walls to a certain height before "dismounting" with a backward flip. It's also possible to jump at the apex of the wall-run to get extreme air.
If there's a ledge at the top of the wall, Aeon will grab it. She can hang there or flip up onto the ledge.
Aeon can also run horizontally along walls. While running, you can stop to drop off, jump to leap at a right angle from the wall, or press an attack button to spring at a nearby enemy.
The horizontal wall run works along corners too.
Ledge interactions are fairly standard these days in video games, but this game has lots of them. You can drop down onto a grabbable ledge from above, leap up from one to another, "run" along ledges and flip from one side of a narrow ledge to the other.
You can also attack from a ledge with a flipping kick that either damages the enemy above you or grabs them and pulls them over the edge.
You can also shoot at enemies while ledge-running. How Aeon's hands remain glued to the ledge while doing all this is hard to say!
Aeon can use her grappling hook to ascend and descend at designated points.
She can also hook an enemy if he's standing near the drop point, which takes him on a wild ride.
Any nearby enemies are automatically targeted if Aeon shoots while traveling up/down.
There are horizontal and vertical poles throughout the game, for reasons unexplained to the player (but the world of Æon Flux is not known for being logical). Aeon can leap between either type of pole, with various animations designed for traveling up, down, laterally and diagonally. She can also launch an attack from a pole if an enemy is close.
Melee combat is not controlled as precisely as in Oni. Instead you essentially mash the quick and heavy strike buttons to achieve combos. You can block on command with a dedicated button, and the enemy can block too.
Aeon can evade with a roll as well as chain an evasion roll into an attack.
Not only can she use a getup attack if she's been knocked down, but the enemy can as well.
Aeon can counterattack with devastating effect if you press the block button as the enemy is beginning their attack, but the timing is very difficult.
The enemy can grab Aeon, but she doesn't seem to be able to do the same to them. Fortunately you can break their grip on you by wiggling the thumbstick.
As Aeon lands attacks, the style meter builds, which allows her to perform a "powered attack" at the end of a combo (though this seems rarely useful). Watch the style meter drop suddenly when she makes her last attack in "powered" mode.
Aeon can finish an opponent who is down to red health using one of four takedowns. One builds her style meter, one throws the enemy, one plants a bomb on him and one restores health.
Shooting is simple, with limited weapon variety. Enemies are largely auto-targeted so you don't need to aim precisely with thumbsticks, an approach that Oni for the PS2 could have really benefited from.
The use of ragdolls for enemies is quite entertaining. This technology was just debuting around the time Oni released, so it's not surprising that Oni lacked it but that Æon Flux was able to take advantage of it in 2005.
For some alternate gameplay to mix things up, Aeon has a small spy tool called an orb that she can deploy at designated points to do tasks that are too dangerous for her, or which require travel in tight spaces.
Somewhat oddly, and not based on the animated property at all, Aeon can also get into a giant ball herself and roll around, attacking enemies. Apparently the use for this is to travel in areas that only a ball can get to, as someone has built lots of chutes and tunnels around the world for some reason.
Another gameplay mode you sometimes enter is controlling a turret, which allows you to take down larger targets with lasers or missiles. Oni could have used some alternate gameplay in order to break up the typical gameplay loop of running and melee fighting.