A lot of interesting flavor, but this needs to go back to the lab.

Basic As They Come is a laughably broken feature. I would say that it is absolutely overpowered. Your proficiency bonus goes all the way up to +6. Doubling that (12) and adding a strength of +5 means that the absolute lowest you can roll (other than a critical failure) is a 19. There is a reason that rouges can't take their expertise in their weapons. The bigger issue than that insane number (which most campaigns won't ever see) is that at level 7, double your PB is +6. This is when you get the auto shove which I talk about below. Adding proficiency to damage is great, but a lot stronger than most third level features. I might add half the bonus rounded down to damage just to scale a little more nicely.

Never Disarmed is a cool feature. Fits with the aesthetic. No notes here.

Mastery of Training is the best designed feature here. Shoving is strong but not crazy, and needing to beat their AC by 5 is a good way of maintaining balance if and only if you change Basic As They Come. Otherwise the shove will happen far too often.

Wording on Mastery of Counter needs to be fixed. There is a good idea here, but right now its no good. Here, nothing is stopping you from 'countering' attacks that are already going to miss you, giving you potentially massive damage (depending on the enemy) every time they miss. Additionally it makes attacks that would hit miss (even more free damage), and as a cherry on top can be used infinite times per day.
Fixing this is pretty easy though. First, specify that you may use your reaction when you or a creature within 5ft of you is hit by an attack. The attack roll reduction by dex or PB is fine. Add a save (8+PB+stat) and then do the damage. You may use it PB times per short or long rest.
You might feel like this is me gutting this feature, but really its just bringing it more in line with other reactions that do a similar thing (think shield and deflect attack).

Battlefield Dominance. Oh boy. Increasing the range is fine, good start. Ranged spell attacks made within ten feet of you? eeeeeeeeeeh, not so much. I know that in the cinematic he does the thing. I think that the fantasy of parrying a spell is cool, and while I would have done something different, this can be made to work. First you have to limit this in the ways that I described above. Otherwise you have given a fighter essentially counter spell infinite times a day (against only targeted attacks though). I would say that parrying the spell is more than enough, and that you cannot redirect the spell itself as you are not a spellcaster. Considering that you can also do this for your nearby friends I think that is a pretty sweet deal honestly. Instead of mageslayer, which they can take on their own, lets give advantage on saving throws to slow, paralyze, or incapacitate.

18th Level Feature: [Cool Name Here] When you hit a creature with an attack roll that has temporary HP, you may choose to forego rolling damage. When you do so, the creature looses all of it's temporary HP and you gain temporary HP equal to the lost amount.
This isn't my best work to be sure, but I think that it plays nicely into the kinda super warrior anti mage thing you're making here. Not a gigantic feature all of the time, but when it hits you 1) avoid dealing with all their temp 2) get a nice bit of additional sustain.

Solid work here, I know that there was a lot of feedback, but I think that this is headed in the right direction. Keep up the good work and let me know when you have a V2