Part: Part Five - Betting Before the Flop

A-K against a three-bet

Pre-flop
Blinds 100 / 200Pot 2,600 (13 BB)COA♠K♦● 25,000 (125 BB)YOUyou opened to 500BTN● 25,000 (125 BB)Aggressive 3-bettor3-bets 1,800 (9 BB)SB● 25,000 (125 BB)posts 100 (0.5 BB)BB● 25,000 (125 BB)posts 200 (1 BB)D

You open to 500 from the cutoff with A♠K♦. An aggressive button three-bets to 1,800.

An aggressive button three-bets to 1,800 (9 BB); you hold A♠K♦. Best?

WhyFour-bet. A-K is ahead of an aggressive three-betting range, so four-betting gets value, folds out his bluffs and weaker hands, and avoids playing a bloated pot out of position. Flatting is passive and folding A-K to a wide three-bettor is far too weak.
What happensYou four-bet to 4,400 (22 BB); the aggressive button folds.  You win a nice pot pre-flop.
Against an aggressive three-bettor, A-K four-bets for value - it's ahead of his range, collects dead money, and sidesteps a guessing game post-flop. The opponent's tendencies (aggressive) make four-betting clearly best.

A-K facing a three-bet usually four-bets - it's ahead of most three-betting ranges and prefers building the pot with initiative over flatting out of position.