I came up with a somewhat broken but hilarious combo using an extrapolation of the degree scaling presented in the document and the earlier Fighter playtest, by assuming that 5th degree maneuvers are gained at 16th level.
With this combo, you can zip around from enemy to enemy, critting them into oblivion without consequence with more attacks than should logically be possible in a six second window.
This is how:
First, pick the Samurai subclass from Xanathar's Guide for its 3rd level ability to use a bonus action to get advantage on all your attacks for the turn three times per long rest.
Second, be level 16.
Third, take Tsunami Dash from Rapid Current and Perfect Edge Stance from Razor's Edge.
Fourth, make sure you have Perfect Edge Stance activated before combat or on a previous turn (-2 exertion)
(Optionally: Have the Mobile feat. Not strictly necessary, but enhances the experience by increasing your speed and negating opportunity attacks.)
Then, the combo commences.
Bonus action: Fighting Spirit (samurai subclass) to get advantage on all attacks for this turn.
Action: Tsunami Dash (-3 exertion). Move at double speed and attack five different enemies at advantage with a 15% crit chance per roll. Not per attack, per roll, because anything from 18-20 on the die is a crit thanks to Perfect Edge Stance, and due to advantage the higher number will always be the one used, so no crit is overwritten.
Since Tsunami Dash only consumes two of the three regular attacks you have at this Fighter level, take the remaining one, too, for two more attack rolls.
Action Surge, Attack action, for three more attacks, adding six attack rolls. (Theoretically you could use Tsunami Dash again with your Action Surge? I'm not sure whether that's possible, but if it is... 160ft of movement (40ftx2x2) 12 attacks at 10 different folks, all at advantage with a 15% crit chance per roll... oh boy.)
Congratulations, you just rolled 18 attack rolls for 9 attacks on one turn, five of those at different creatures, four at anyone you wish, each roll having a 15% chance to crit, moved double your speed (80ft if Mobile feat), and can do all that two more times before short resting, three more times if the final time is a separate combat from the previous (so you regain one spent Fighting Spirit use upon rolling initiative.) And if you have Mobile, anyone you swung at as you zoomed by with your 80ft speed cannot even AoO you.
If this skeleton is combined with a weapon with a large die (like a d12 greataxe), crit-enhancing features or abilities (like a half-orc's Savage Attacks), damage-per-attack bonuses (such as a die-based weapon buff such as Elemental Weapon or Holy Weapon), or effects that grant additional attacks (say, Haste), it gets kind of ludicrous.
Combining all of those, you would move 80ft, make ten attacks at 1d12+2d8 each, which provide twenty opportunities to crit at a 15% chance, for 3d12 plus 4d8 damage each, in one turn, while ignoring AoO from anyone you attack at least once.
The only limitation at that point are the abundance of your party members' spell slots to cast Holy Weapon or Haste, your own exertion pool (though with the ability to do this four times a short rest if it's all you use your exertion on, it really isn't much of a limitation), and the requirement that half your attacks be targeting different enemies. Otherwise, as long as your foes are standing on the ground (or you can fly someway), within range and you get to your initiative before being crowd-controlled or dead, you will eat the enemies' hit points like a black hole. A very, very speedy black hole.
I hope you enjoyed my insane little experiment.
I had a lot of fun playing around with these maneuvers to come up with this broken build, in the attempt to create a fighter flavoured as a time-bender. Though many maneuvers feel overcosted or need a buff because they're too situational or underwhelming, it's already clear what potential this has and I can't wait to get my hands on the final version.