Basically, after undertale Frisk chose to fuse with Asriel and the little bit of DT and energy left over form the final battle. This along with having full control of their soul and flowery's base power and determination, makes them the strongest being alive,probably comparable to Ink!Sans.

  
They live with Toriel and was raised by her and other monsters. They are the ambassador of monster kind and deal with Monster-Human relations, as upon being freed, they faced extreme discrimination and were almost segregated. Of course frisk stopped that at its root and is constantly doing more and more to fight against stuff like this, not just against monsters, but also against humans by monsters and other humans.

  
Frisk is playful, optimistic, generally silly, flirty, and of course, filled with determination. They love pies, specifically snail pies.

  
Their abilities consist of

Bullet patterns based off of each soul, as well as stronger versions of Omega flowey's bullet patterns, along with some of Asriel's and Flowery's.

Gravity manipulation

Super speed

Super human endurance 

Super human strength

Teleportation

Reality manipulation

SAVE files

All of the soul abilities

Choas Sabers

Choas Blasters

Vine manipulation

Flower Manipulation

Combat expertise

Summoning and use of the Hope Knife, a weapon that does karma damage and has 99 DMG

Still has the Heart Locket

They can leave their Reality at any time.

Lightning manipulation

Fire manipulation 

There's more I'm forgetting but it doesn't truely matter

FUTURETALE Frisk, The Ambassador Of Monster Kind