Base Class: Fighter
Dreadnoughts are fighters known for their great strength and constitution. Trying to harm them will only hurt the attacker. Few can say that they have defeated a dreadnought in any form of athletic activity. However, this doesn't mean that they are invincible, just that they are hard to kill.
Armor Training
At 3rd level, while you are wearing medium or heavy armor, you ignore disadvantage on stealth due to the armor, and you gain a bonus to your armor class equal to your proficiency bonus.
Earth Breaker
At 3rd level, you can use an Action to slam the ground with your fist, leg, or your weapon to shake the earth. Any creature within a 5 ft. radius of you must make a Dexterity saving throw DC equal to (8 + your Strength modifier + your proficiency bonus). On a fail, a creature is knocked prone. You can use this ability a number of times equal to your Strength modifier. You regain all expended uses when you finish a long rest.
The radius increases to 10ft. at 7th level and 20ft. at 18th level.
Dreadnought Resilience
At 7th level, when an enemy critically hits you, you can treat the critical hit as a normal attack. You can do this a number of times equal to your Constitution modifier after each long rest.
Third Wind
At 10th level, after using Second Wind to regain hit points, you can use another bonus action on your next turn to regain hit points equal to 1d10 + half your fighter level.
Stone Hardness
At 15th level, when you are forced to make a saving throw against being grappled, incapacitated, paralyzed, knocked prone, restrained, or stunned, you can spend your reaction to gain advantage on the saving throw. Additionally, if you succeeded on the saving throw, you can also make a melee attack against the person who forced you to make the saving throw as part of the same reaction.
Unrelenting Will
At 18th level, you gain advantage on death saving throws. Furthermore, when you are reduced to 0 hit points but not killed outright, you can choose to gain hit points equal to half your fighter. You can’t use this ability again until you finish a long rest.