Protector

You trained to become a protector, defender of the weak and innocent... or just your teammates, ya know evil people exist and might want their evil friends take less damage.

Level 3: Taunt

You taunt the enemy, forcing it to make a Charisma saving throw (DC = 8 + fighter level + proficiency + Charisma modifier.) giving it disadvantage on all attacks against targets that aren't user, as well as making them unable to use opportunity attack on anyone but the taunter. The target can reroll the saving throw at the end of it's turn.

Level 3: Remarkable Athlete

Thanks to your athleticism, you have Advantage on Initiative rolls and Strength (Athletics) checks.

Additionally you add half your Con modifier to your initiative rounded down.

Level 3: Combat Stances

As a Bonus Action you can go into a defensive stance or offensive stance. In defensive Stance you increase your AC by +1 if you're wearing a shield, +2 if you're dualwielding two Onehanded Weapons or +3 if you're wearing a Twohanded weapon.

In defensive stance you have disadvantage on attack rolls, enemies also have disadvantage on attack rolls against you.

Offensive Stance lowers your AC by -2, but you have advantage on attack rolls and get a +2 to attack and damage rolls.

Level 3: I will be your shield!

You throw yourself in front of an attack within reach that hit an ally, taking the attack for them. Lower the damage by your level + proficiency bonus.

If the attack you are taking for an ally, is a critical hit, you take the full damage instead.

Level 7: Additional Fighting Style

You gain another Fighting Style feat of your choice.

Level 10: Defensive Bulwark

You are mastering the art of defense. Through vigourous training you bolstered your body to take more hits. Add your Con modifier to your AC, additionally you can use your reaction to lower your or the damage an ally you can see takes by your Fighter Level + Proficiency + Con Modifier.

If you used your reaction to use "I will be your Shield", you can use Defensive Bulwark without needing a Reaction.

Defense Master

Once per Short Rest you can make a Critical hit that you tank for an ally using "I will be your shield" a none critical hit. The attack still hits it just doesnt do Critical damage.

Guardian

Once per Long rest you can use a Bonus Action to use all your might to withstand attacks. For 1 Minute all attacks against you deal half damage, but your movement speed is rendered to 0. teammates around you (up to 10ft) gain a Bonus to saving throws equal to your Proficiency Bonus and if they are behind you whilst making a saving throw against a damaging spell they take half damage of that spell.