Okay, let's see.
Speed:
There's this guy in Dragon/Tiger Gate named Tiger Wong. Main, Gary-Stu character. Now, he does stuff like 'blitz people who catch bullets between their fingers'. Ancestor fights evenly with him (speedwise - he trumps him elsewhere). Lest we consider that 'fighting evenly with' is not indication of speed, Tiger takes it a step further. He attacks Ancestor using one of his specific 'speed' techniques that allows him to kick dozens of times in an instant. The scene shows him multi-striking Ancestor all-out, multiple afterimage legs in a single panel and about fifty flashes of impact all around Ancestor.
Who blocks all of the attacks, then damn near kills Tiger with the following counter.
Pretty much everyone in the comic is insanely fast (Tiger being the fastest, it's like a shonen comic that way) and Ancestor tends to blitz the crap out of most people when he gets serious.
Right, another speed-feat. There's this other guy who controls a demonic sword. Can send it flying around, remote control (Ancestor does this as well, but he just does it, doesn't need any demonic thing happening). The guy sends it after this monk. The monk can't deal with it - it's drawn like a lightning bolt flashing through the air (edit: worth noting that just it flying through the air is ripping up the ground a yard beneath it), and it's just too fast and powerful. So he puts up an Omni-directional shield.
Note - this sword is attacking him through the ground, burrowing through granite at one point with no appreciable loss of speed.
So the sword hits the shield. It's pushing into it. The wielder leaps forward and smashes his palm into the hilt, punching it through the shield. It zips in at that crazy speed at the monk's neck, inches away....
Ancestor does this 'appear out of nowhere' thing and catches the sword with his bare hand. He's nowhere in the area before this - first we see of him.
I guess I should mention...he flies. Fast enough to intercept 747's (which he then shatters in half in a gigantic explosion with a palm strike).
If I think of more speed feats, I'll mention them.
Striking power.
So, blows up 747's. That's the least of it.
There's another character - crazy, crazy powerful. He spots a friend of his about to get smooshed by a falling rock larger than a house (no joke, this thing is huge - the character is the size of a large ant in the frame). He leaps in and obliterates the boulder with a Edit: Palm strike - thousands upon thousands of tons (it's at least somewhere around 10mx10mx10m or larger, and that's at least 3000 tons if it's 'just' that). This guy later tries to stop a falling meteor that's somewhere between the size of a hill and the size of a mountain. The effort almost kills him, but he barely manages to 'deflect' it somewhat (rather than destroying it or stopping it - he more 'shifts the angle of its fall)', which is an absolutely crazy feat.
Ancestor beats this guy down.
He throws energy blasts that catch people and fling them against granite hillsides, leaving a giant Buddha's palm impression in the hill (like in Kung Fu Hustle, but in granite). He hits flying people hard enough that they arrow downward and, upon impacting with the ground, create an explosion hundreds of feet high and destroy a hillside of the same height. He hits Tiger Wong with a palm strike and the clouds a mile behind the hero just part, a hole punched through them. Guys who can fight for pages and pages against people who bust multi-ton boulders, he crushes with a single attack, or splits their head in half, or.
There's a scene where an enraged Tiger Wong, gone into a heroic fury, attacks him full-bore. Ancestor blocks the attack, and it still causes the earth to shatter into car-sized boulders for about a hundred feet in every direction.
Ancestor hits harder than Tiger. Explicitly.
Gotta head out, but I'll get to durability (haha), regeneration (on top of the durability), special abilities (dude is a swiss-army knife of things), and his sword use, which deserves commentary on its own (dude used to be known as The Invincible Swordsman in another comic, set 80 years previous, and with good reason).
Durability.
Ancestor's durability is insane even for this series. He consistently eats hits from people like Tiger Wong, Tiger being a dude who (as noted) when completely enraged can shatter the ground for fifty to one hundred feet in every direction, said ground heaving up in car-sized boulders (not SUV, but normal car). Dude named Barbarian is roughly on that level for hitting power, Ancestor powers through his hits. These things cause him anywhere from minor to major damage (usually minor, sometimes they catch him with something good). Another powerful dude stabs him through the chest - not gut - right at the solar plexus, just under the sternum. Punches a palm-wide swordblade all the way through him, so that Ancestor is impaled. It...doesn't slow him down at all, and he doesn't seem to care it's there. Ancestor proceeds to treat the guy like a child with the blade still sticking through him the whole time.
Then there's his Regeneration.
There's one scene where Tiger has gone bonzo (the 100' radius blasting thing). Him and another super-kung fu take on Ancestor and actually manage to get the upper hand. Tiger goes absolutely crazy on Ancestor, beating him consistently with strikes on the level of the one I mentioned, finishing it by smashing down the side of a mountain, Gandalf-versus-Balrog style. Ancestor travels the entire way down, bouncing into and breaking the mountainside on the way down. He hits. There are some X-ray images showing his skull to be shattered, and by shattered I mean 'into splinters the size of my little finger' (it's more cracks than it is solid). He's also busted up like nobody's business elsewhere.
Tiger attacks, Ancestor still blasts him away. Ancestor then pretty much 'flexes his qi' in a massive burst that, once again, makes the area explode.
He's then fine. 100% cool, fully healed. His followup attack on second dude (who was doing almost as well as Tiger) kills the dude instantly, he wrecks Tiger, then he falls victim to one of his 'Evil Kung Fu has corrupted my qi!' headaches and leaves the battlefield in agony, smashing through a granite cliff as he flies away and not even noticing.
This is a pattern that happens throughout the series. Ancestor treats everyone like trash. Something happens such that he actually gets hurt. Everyone dogpiles him. Ancestor gets more hurt. Ancestor flexes his inner power. Ancestor is fine. Ancestor wrecks the entire group and either leaves to deal with other business, gets his attention taken up by someone else (whom he kills), or whatever to keep him from just executing everyone.
The guy is pretty much unstoppable.
Another durability feat. That scene with the monk fighting the guy with the demon sword. That sword burrows through rock effortlessly. It's also later shown to corrupt anyone it cuts, the demon possessing them or something (it just NICKS a guy's neck and he gets possessed). Ancestor appears out of nowhere and catches it when it has the power of someone ELSE hitting it on top of its normal rock-burrowing attack power and speed. He catches it by the blade. In his bare hand, fingers wrapping around the edges (like he's gripping a rod, only it's a blade). One-handed, arm extended, effortlessly.
And explicitly stops it dead without getting cut. Speed, strength, and durability right there.
Special abilities...
Well, he throws all kinds of qi blasts, from stuff shaped like his palm, to lances of energy, to huge DBZ style things, whatever. They ruin the day of anyone they hit and destroy huge tracts of land. Right after he blows up a jumbo jet, he pauses, sees something interesting on the horizon. Only the clouds are in the way. So with a simple wave of his hand, he sends out a massive blast of energy that basically opens a multi-mile long chasm in the clouds so he can see what's what.
As Nik mentioned, there's his Thousand Escaping Poisons thing, where he can emit enormous clouds of poisons from his body to surround him, or to snake out under his control and surround someone else, or to poison people he hits. This poison kills normal people instantly (turning them to dust and ashes), crumbles ancient trees in about the same time, and literally rots stone. It also wrecks these super-martial artists whose qi normally protect them against poison.
He flies. Like, really fast. And also fully controlled. When the guy stabs him through the gut, he grabs the guy by the face, laughing, and speeds downward from on high (they're fighting from miles up). The guy is screaming at him to stop, they have a short conversation, Ancestor obviously has the intent of planting the back of the guy's head in the rock below (they start off so high that mountains below them look like 'geography', and in that short conversation - a page, at most - they're at the ground). The guy surrenders when his head is about 2' from the rock and...Ancestor reacts perfectly and stops dead, right there.
Also, he appears immortal. He dies. He comes back to life a couple of panels later. And whales on everyone involved.