In this new NBA 2K21, there's a multitude of different power forward builds you can make, ranging from a paint dominant scorer like Zion to an all-around threat like Giannis. However, the best overall build for both MyCareer and Park will be the Stretch Four, similar to Anthony Davis or Kevin Durant.
Creating a Strech Four build allows you to dominate your opposition, especially in the Park. You have the ability to hit both open and contested threes at a high rate, and since you are a power forward, you are still able to get points in the post if a smaller defender is guarding you.
When you're not knocking down open threes, you being on the three-point line will force your defender, most likely a power forward or center, to get out of the paint to guard you. With the opposing big man away from the rim, your teammates will be able to get relatively easy layups and dunks without the threat of being blocked. And if the big man does leaves you open, with the shooting ability of a stretch, that's an easy bucket.
To go along with the offense, you will also get ten defensive badges to help you hold your own against opposing players. Your height will allow you to get defensive rebounds, as well as block shots, or at the very minimum, get a good contest.
The ideal height for this type of player is 6'10. This will ensure that you are tall enough to play defense and rebound efficiently. While this will drop your shooting to about an 80, the shooting badges that this build gets will make up for it.
In the new NBA2K21, the Stretch Four is by far the most overpowering and all-around best power forward build to play with.