Re this video of Mcgregor's beatdown of Aldo where was the knockout punch?

Re the knock out video his hands are moving so fast it looks like (to me) he barely touches him and yet Aldo starts toppling so fast it almost looks like he’s tripping. What was the (standing upright) punch combination that connected?

Not sure what you mean by combination, it was just a straight left. At 9 seconds Aldo plants his feet and goes for a big left, he opened up and McGregor nailed him on the chin before it even landed.

Both punches landed, but McGregors hit the right spot. Had Aldo’s landed a few inches lower McGregor might have been in trouble as well but as it was he shrugged it off easily.

Yup, the left caught the guy coming in. Reminds me of Prince Nassim Hamed.