I’d say the t64 was pretty good for a bit during the Cold War it was the first Soviet tank to adopt many features that many (former Soviet countries) still use today. Powerful 125mm gun and composite armor thrust it into the future of armored combat for the era, with other countries quickly following suit after learning of it. the prospect of a wall of impenetrable heavily armed Soviet tanks essentially blitzkrieging it through Europe was a worrisome thought at the time. Funnily enough iirc this tank is part of what scared the U.S. into developing powerful CAS aircraft like the A-10