Aatrox is a unique character because of his gruesome strength matched with low health to begin. He can be overpowered just like any other champion, but only if you build him correctly and use him wisely. At the beginning of the game he is an expert assist creating machine. His knock up can allow early game ganking and charging to be unstoppable. The combination of ignite and flight will allow you to close gaps and kill those who run. If you time your moves correctly even at level one, you will be able to turret dive if and only if they have less than 25% health and you have over 50% preferably 75% because by the time the turret can do any true damage you have slain the enemy or at least placed ignite to finish the job and blood well will be able to save you from the turret death.

He has multiple pros and very little cons, but the cons can be detrimental unless taken care of quickly.
Pros:
1. His blood well ability can help you make a quick get away, especially early in the game with flash and flight.
2. The combination of blades of torment and flight can be truly devastating to enemy champion so long as your fellow champion is paying attention.
3. Early in the game if you can communicate with the lane sharer you can devise a plan to not only knock up with flight, but hopefully you are sharing a lane with someone with a stun, slow, or knock up ability as well to quickly kill the first victim even if there are two enemy champions.
Cons:
1. Squishy in the beginning.
I. Follow the item build precisely and you will not have to worry about being squishy by level 12.
2. Flight takes away 30% percent health in the first stage, so use it only on champions.
I. This is why I recommend to max this ability out as quickly as possible, because by the end it only takes 10%.