There are alot(not realy, there are like 5) places in which you can achieve such a high combo. The easiest and most consistent one is in "The First Dream - Prologue", which just so happens to be the level you HAVE to do in any speedrun (How convinient :D).

DISCLAIMER: If I write "he" im referring to the Shambler. (German Grammar puts things "it"s into genders... so im writing he)

The setup involves the 7 Shamblers at the first big opening, after the mini-tutorial. After you've passed the first 3 Shamblers (2 without AI, one with), don't hit any Shambler!!! This is very important. Kicking is the only thing which doesn't deal damage. (For practising the setup, I highly recommend placing a checkpoint down on the floor after you climb up from the room with the AI Shambler)

Next up is grouping the 7 Shamblers which shamble around the area. Start with the ones at the right (3). Kick the first one to the left. He might go down completly, in this case ur done with him. Or he hits the ceiling and lands on the little platform below which is not the floor. If this happens, kick him left again. Kick the second one left, when he's on the left half of his platform. If he dies in the pit, he wasn't left enough => Suicide, try again. If he lands where the first Shambler was, do the above mensioned for this Shambler again. Kick the third Shambler to the left, when he's on the left half. Pretty much the same as the other ones.

I recommend doing these first, as it lowers the chance of a Shambler bouncing of another one into the pit where you climb out of in the beginning.

The 4 at the top have different strategies: The one on the right wall needs to be kicked right when he's as close to the wall as possible. He should hit the side of the little platform the 3rd from the left is standing on. The 3rd from the left needs to be kicked left when he's as close to the wall as possible aswell. He should hit the ceiling bump of the platform on which the 2nd Shambler from the left is standing on, and should fall down. For the rightmost Shambler, wait untill he is roughly lining up with the tunnel leading up to the 2 Bomb Imps. I recommend to beginners: Hang onto the left wall of that shaft, as soon as the Shambler is a bit left of the wall, slide down and kick. If he lands on the platform of the 3rd Shambler from the left, your good to go, do the same thing as before with him. If he lands on the platform he and you are already on, wait and try again. If he lands on the platform with the 2nd Shambler from the left, AND doesn't knock that one into the spikes, kick him to the right and try again. If he lands on the platform with the 2nd Shambler from the left, AND does knock that Shambler into the spikes, Suicide and try again.

Now you should have 7 Shambler shambling around on the bottom floor. I recommend saving at this point again (You can get enough blood with the blombs, and the Shamblers even further right)

Now, after you've done the setup comes the execution. Start on the right. kick all the Shamblers left. Run left, kick all again.

Your goal is to hit all Shamblers into the pit you came out off, before they are unstunned and beginn to run around again. Hit all Shamblers into the pit, jump down, Highkick (kick all up). Hold up, and hit attack TWICE. Wait a tiny bit. Kick up, attack upwards twice again. Now look left, and just kick. All should die to the spikes and you should get a 70 Combo.

Video: tomorow, 3 am is late D: