Villain was 25/10 over 15 hands. No other reads.

Full Tilt Poker $0.50/$1 Pot Limit Hold'em - 6 players

BB: $68.50
UTG: $101.50
Hero (MP): $106.40
CO: $90.65
BTN: $108.10
SB: $108.00

Pre Flop: ($1.50) Hero is MP with K K
1 fold, Hero raises to $3.50, 2 folds, SB calls $3, 1 fold

Flop: ($8.00) 4 5 6 (2 players)
SB bets $4.50, Hero calls $4.50

Turn: ($17.00) 6 (2 players)
SB bets $12, Hero requests TIME, Hero calls $12

River: ($41.00) J (2 players)
SB requests TIME, SB bets $30.50, Hero calls $30.50

On the turn I decided to call a blank river. Should I raise at some point?

this is fine raising sucks nuts. id rather fold the river than raise anywhere.

Donking is usually a polar range spot. Although this flop is dirty its a bad spot to raise, as we want his air/weak pair hands to continue and raising kills that.

I would actually consider folding river vs most villains in this spot, you have to put him on an a complete bluff, or a strangely played mid pair.

Actually I am ok with your line..and I dont think his betting range is that narrow here.. J is an ok bluff card if his diamond/combo/whatever draw missed

His bet sizing is pretty weak so I would call down. I wouldn't say his donking range is polarized as many people will do this with overpairs and good draws. He also might have hit the J for tp and be value betting it.

can't fold river b/c he can vbet worse (Jxdd), or be bluffing, and your hand is underrepped.

heh, and this is why donking can be such an annoying strategy if you're IP. I mean it sounds like we don't know anything about him? Did you check to see if he was multi-tabling at least? I'd rather just know if he's a reg or a fish. If he's a total unknown, I'm just going to call down. he can definitely be donking pair + draws, FDs, two pairs, sets, 77, etc. I think a random opponent can have a fairly wide flop donking range on a board like this.

I'm definitely calling the river as every draw missed. So his value range is down to 67/65/55/44/78. You're getting a good enough price imo considering how often I think he'll have missed draws on this board texture.

i dont wanna fold the river :P just saying, thats better than raising somewhere.

I would raise the turn. His range is so wide and has a lot of draws in it. You can stack overpairs, get more money out of combo-draws and you get stacked by full houses which are like 10% of his range.
As played, the river is a snapcall.

He's 25/10 over 15 hands, he definitely can have sixes in his range as well.