The A10 is an amazing aircraft - proof that the "best" is a relative term that entirely depends on the requirements. The A10 is the right tool for the job.
There is an almost endless number of weapons specifically designed to kill armored vehicles. These all came out of the "Fulda Gap
" scenario where masses of Soviet tanks were going to pour through the Fulda Gap into Europe. The West was going to be hugely outnumbered, so tank vs tank would never be close to 1-on-1. Each Western weapon had to be capable of killing numerous Soviet tanks.
In addition to the A10, one of my favorites that came at the end of the Cold War was the "Brilliant Anti Tank" (BAT) submunition. It could be fitted into cruise missiles and other platforms - the Tomahawk or ATACMS could carry over a dozen BAT vehicles. It has acoustic & IR sensors, and a shape charge warhead. The cruise missile spews them out at a high altitude, then each BAT autonomously finds a target, locks-on and kills it. Almost impossible to defeat, and deadly accurate. (When it works - testing was a mixed bag) BAT was deployed, but I don't know if it was ever actually used - it was delivered after the Iraq turkey shoot, so I think it missed it's time to shine.
So, picture this: You and your buddies are sitting in your bad-@ss main battle tank, surrounded by 100 other bad-@ss main battle tanks. You are the meanest mofo in the valley! Meanwhile, hundreds of miles away, a couple of Navy destroyers each fire 6 Tomahawk cruise missiles. An hour later, you and all 100 of your bad-@ss mofo friends explode - each of you blown to he11 by this:
Trust me - the LAST place you want to be when the bullets start flying is inside a tank!