Hero (500) opens 10 with KQ from MP.
Villain (500) 3bets to 28 from BU.
Hero folds.

He's a good aggressive reg that adjusts his game to different opponents a d polarises vs hero. I saw him doing it once with K4s, hero folded and it went to showdown with SB player.

What's my strategy here? Should I adjust by 4 betting bluff KQ here? (and hands like KTs, KJ, QJs, 99?).
Which do I fold?

Just fold. Its a cash game, so you can always seat or table change if this guy is consistently targeting you with 3bets. Calling 3bets out of position is so -EV and high variance. Cash games are so soft that you really shouldn't be caught up in these d**ck waving contests. If you find yourself at a table with light 3-betting then you should consider finding a new table where opponents are more predictable.

Huh? If he is 3 betting weak hands such as K4 vs you, then you would be 4 betting KQ (and the other hands) for value.

It's kinda important to know exactly how the K4 hand got to showdown. Did he 3 barrel bluff it? Did he make 2 pair and value bet it all the way? Or did it just check down after he raised pre?

If he would fold trash like K4 to a 4 bet, then no, we don't wanna 4 bet him. If he is the type to bluff after 3 betting preflop, we will just need to take a better range than him and grit our teeth and call down. It kinda depends on how he plays postflop.

i play similarly to him so the only insight i can give you is that i will 3 bet pots that i have a reasonable likelihood to pick up preflop regardless of my cards but also paying attention to my image at the table. if i have been card dead for a while then i'll try to 3 bet pick up a pot that is ripe.

i don't know about V but my 3 bet range is balanced and weighted towards premiums like 80% premiums so 4 betting me light is a horrible idea. i don't think there is much you can do here and the real question is: does this happen often enough for it to matter? probably not.

I don't like much of what is said in this post, but I really, REALLY disagree with this as a blanket statement.

As far as "all or nothing" poker axioms go, I feel like "not calling 3!'s OOP" is one that is worth it's weight in gold.

Unless you are sufficiently deep, or on the flipside, flatting deceptively with AA and a low SPR pot, I don't really see a benefit to calling > 4! OOP.

What's your thought process here?

If V is polarizing his 3-bet range, then 4-betting KQo would be horrible.

With a 4-bet, you'll just get V to fold hands you beat (the air part of V's polarized range) and continue with his stronger hands (the nutty part of V's polarized range).

Against a polarized 3-bet range, you can flat with a merged range including KQ. It will be difficult to play oop, which is one reason why 3-betting the polarized range can be so effective, and I'd much rather have KQs than KQo, but flatting is way better than 4-betting. If K4s is in his polarized range, you're doing pretty well here.

Generally, tighten up your opening range a bit and flat a pretty wide value range oop, and I would put KQo squarely in that range. I would consider 4-betting much weaker hands (villain will be 3-bet/folding with some frequency, and you can turn weaker hands into profitable hands) and flatting with some very strong hands, especially if V continues with a wide 3-bet range on many flops. You could just polarize your 4-bet range, but I'm OK 4-betting mostly the weaker hands in your range to start and then you may need to adjust.

Bottom line, think about V's polarized range and what he'll do with his hands. You'll see 4-betting KQo is a mistake and a losing play - V folds hands you beat and continues with hands that beat you. You also need to think about how wide or narrow his range is and what he's 4-betting in certain situations. If you think this is a situation where K4s is in his 3-bet range, then his polarized range is probably overweighted to weaker hands against which KQ has excellent equity; by all means call pre and imo very likely peel some flop bets.

My post explains his thought process. Yes, against the majority of live villains, don't call a 3-bet oop because they have a nutty merged 3-bet range (i.e. JJ+, AK). In this case, villain is polarizing, so it's a totally different situation. Given the K4s history, it's also possible - but not certain, we need a better read - villain's polarized range is weighted possibly heavily towards weaker hands.

It really depends on the 3 bettor. There are plenty of Vs that I am happy to play against as 3 bettors, they are so aggro post that position is less of an issue. If I knew more about how the K4 hand got to showdown, I might be happy to play KQ vs this V, IP or OOP.

EDIT: And ty, Willy, you did say it better than I did.

Ha, thanks. I didn't want to put words in your mouth, but I was pretty sure we were 100% on the same page!

Is 4-betting really that horrible? We're blocking two of his premium hands. Villain is going to be put into a tough spot post with the rest of his value range as our line looks so strong (assuming we don't have a fos image), except for AA which he probably 5-bets, allowing us to easily get away.

We fold out small aces and small pp he is getting fancy with that have an equity advantage against our hand. Sure we have K4 and Q5 hands dominated but those hands are going to put us in a lot of tricky situations as we are oop. I'll happily fold out the rest of his range that we are currently ahead of (56s, 79s, etc).

If we had position I'd be much more inclined to flatting the 3b and playing poker.