Site is Bovada so HH's don't come in until the next day. Villain is standard 24/18ish over only 20 hands. Hasn't faced a 3bet yet. My 3betting range is around 13-14% so A4s is a standard 3bet for me here:

Hero dealt A4s (SB), all folds, CO raises 3bb's, Hero 3bets 10bb's, folds to CO and he flats.

Flop KhTs7c: Hero bets 2/3 pot, CO calls (I think my cbet might be a mistake, I justified it because I had backdoor FD/Gutters to fire).

Turn 9s: Hero barrels $13.25 into $20ish pot.

River 5c brick: Hero ships $22. Villain calls.

For getting to this river this is the bottom of my range. with anything I've 3bet minus a3s and a2s - 1 combo of each. I feel like it's spew and that my big mistake was cbetting this board texture that will hit villain pretty hard. Thanks for the help guys!