People don't understand aatrox. If you are getting "instabursted" lategame, that means you haven't adjusted your playstyle to your build and your team.
Before i start my explanation of how you play aatrox, I'm going to tell you the most important thing not to do... DO NOT initiate fights. That is why you are being instabursted.
There's four key aspects to keep in mind while playing aatrox.
What is your team comp like? Did you get fed? What is their team comp like? How did you build
I usually wouldnt bring aatrox onto any team that doesn't already have a strong initiator tank(Amumu, Mao, Leona) because it forces you to build very tanky so that you can take on the role of a tank, and that isn't his strongest role. if this is the case, you have to keep in mind that just because you are built as a tank, it doesn't mean you just jump into the enemy team whenever you can land a q, you will usually need to wait for your mage to make a pick, or counterengage on their tank with an effective bork frozen mallet combo. Whenever i build this I consider myself the guardian for my team. When the enemy tank/ bruiser/assassin jumps in, I q them, pop my ult, and slow them with my e and auto's. This gives your team plenty of time to position, and focus the now perma slowed attacker, while you are probably at the front of the battle. You will be tanky enough to outlast him with your randuins, spirit visage, possible GA and heals. you can now turn on the enemy( you will probably die, but as long as you CC'd the enemy carries after you killed off their first attacker your team will probably be able to kill the valuable targets with their tank killed off, and you come back to life, ready to disrupt the enemy in the final stages of the battle.
Did you get fed? I win my lane 90% of the time with aatrox so probably, yes. Your first item should always be either a hydra or bork. I'm not sure how to explain when i decide to go which one, it just depends on who you're lane matchup and how the enemy team comp is. If you are fed, the second item is crucial to how you will develop into the lategame. I look at my team and i say, ok does my team need utility? frozen mallet as a second item will provide lots of utility will also helping me snowball the midgame with extreme chase potential. Is the enemy team naturally beefy? last whisper. Do you need to be tankier? I like to buy just the wardens mail for the armor, and then complete spirit visage. It gives you all around more solid defenses while also increasing your heals. Is your team lacking in physical damage in general?(ex. blue build ez has lots of utility, but doesn't put out as much upfront damage as a vayne.) I might build a phantom dancer or an IE(IE only if you have bork instead of hyrda) This is going to give you all the damage you need, but you need to keep in mind that until you get some tanky items, you will pop like a balloon if you get focused, so you need to use the range from your ult to your advantage in teamfights. Never jump in unless the fight is almost over.
tldr if you think aatrox isn't good you probably haven't put in the time to learn what you should and shouldn't do with him.
?
