Your ancestors were members of the race of alien warriors known as the Sayajin their blood flowing through your veins gives you a lust for battle like no other and augments your strength to insane levels. Their blood allows you to control Ki in ways no other race can. 

[Disclaimer: This subclass was made for fun and is meant to be extremely overpowered. for the love of your DM please don't use this or at least make sure they know exactly what they're signing up for if you do]

Ki blasts

Starting at level 3 whenever you make an unarmed strike as your attack action you can choose to instead spend a ki point and make a ranged ki attack against a target. This attack does force damage equal to your martial arts die and has a range of 90. After your first ki blast attack you can make a second ki blast attack as a bonus action.

Flurry of Ki

After firing a Ki blast as a bonus action you can spend Ki points to fire off even more Ki. For every Ki point you spend you fire off 2 more Ki blasts.

 

Sayain Blood

At level 6 your Sayajin blood has boils in battle and now refuses to rest. In battle whenever you miss an attack roll you can reroll that attack, also as a reaction to a melee attack against you you can roll a contested d20 + your Dex + your proficiency bonus against that attack and,  on a success block the attack and counter with an unarmed strike. Whenever you take a rest you spend as much time as possible training your body. This greatly augments your strength as you continue to level up as shown in the table below. you also gain a flight speed equal to your movement speed.

[Disclaimer: I have no idea how to alter your monk damage die in dnd beyond so you'll just have to manually make a lot of your rolls from level 9 on]

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Sayajin Martial Arts

lvl 9 | 1d8

lvl 12 | 1d10

lvl 15 | 1d12

lvl 18 | 1d20

 

Ultimate Ki Blast

At level 11 your manipulation of Ki grows ever stronger. As an action you can spend any number of Ki points (minimum 3), until your next turn you gain that number as bonus ac while you charge up a devastating attack. On your next turn make a ranged attack against a target dealing force damage equal to the amount of Ki points spent to charge this attack rolled as martial arts die. 

This attack and the stance your character takes when making it is up to you. You can choose to do the basic Kamehameha stance and attack or fire off a galick gun or even a final flash, or you can make your own technique and mimic the stance for your friends, you might look dorky but  I'm sure it'll be fun.

Super Sayain

At level 17 your Ki rages and Sayajin blood boils as your strength reaches even greater heights. As a bonus action you can begin going Super Sayain. You can spend a number of Ki points (but not all of them) and boost your AC by that number until the start of your next turn, or you can choose to save your Ki points but if you get attacked before the start of your next turn you'll have to roll a con save, DC = Ki save DC, or fail your transformation. At the start of your next turn you enter Super Sayain form. While in Super Sayain form; your Martial arts die becomes a d100, your basic Ki blast attack costs no ki, your movement speed is doubled, you gain a +4 bonus to your attack rolls, and you gain resistance to bludgeoning piercing and slashing damage. Super Sayain lasts for 5 minutes as long as you still have Ki and are conscious. Should you use all your Ki to charge up an Ultimate Ki blast you'll stay in Super Sayain form until your attack is fired, whether you hit or miss you'll return to your base form. Once you leave super Sayain form you loose half of your remaining Ki (if you still have any) and your movement speed is halved for two turns.