top set river spot vs unk $2

1/3 $900 effective. im doing my usual thing which is being a nit.

$6 straddle

i make it $20 with KsKh HJ, button, straddle calls

Flop Qs4s2h checked to me i bet $20, button folds straddle calls

turn 6c straddle checks i check back

river Kc he checks i bet $75 (i think a mistake, $50 would be better). he c'r to $500?

hes a younger guy, in his 20s. laggy pre. havent seen a big bet from him b4 like this.