In the new open beta, this is the tank with the most armour possible that can be made with the no step back tank designer : r/hoi4

Hearts of Iron IV - Allied Armor Pack DLC Steam CD Key

Hearts of Iron IV: No Step Back - Paradox Interactive

The best Hearts of Iron 4 DLC

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KR - Tanks for Everyone - Skymods

You have to chose a tank from 1941 onward and make it be able to go toe to toe with today's modern tanks. Conventional upgrades (i.e. better penetrating gun, better armor, etc.)

Download mod «Expanded Tank Designer» for Hearts of Iron 4 (1.11.8)

Best Ship Parts in Starfield, How to Upgrade Ship Parts & Skills - EIP Gaming

HoI4 DevDiary - Tank Designer

Fixed and Bigger Tank Models - Skymods

NEW Update RUINS Tank Destroyers! - HOI4 No Step Back Tank Designer Guide

Hearts of Iron 4 (HOI4) – Which DLC Is the Best? - Gamer Empire