Other than the obvious about the ppe ( a hardhat being the absolute minimum - especially with visible rot )
1) not putting the tree in front down and putting a much heavier tree down on top of it amongst high-stumps (fatalities)
2) sloping notch ( ditto )
3) not having a clear plan of exit ( ditto )
4) Felling onto high-stumps ( ditto, and wasteful too)
5)Getting over excited ( most likely ditto, but who knows-you can't ask )
6) It doesn't look like you have someone nearby to help you out if something goes wrong. This is good practice at all times, and is critical when you are unsure of what you are doing (ditto )
There's a few other ditto's in there but I decided to be generous.
Congratulations, you have three lives left!
Seriously though, I hope this video was done for instructional purposes only. If so-kudos to you. If not- best go do some reading so you can make a safer video.