Stukov Default

Level 4

Vigorous Reuptake will generally put out the most stats through the course of the game.

Biotic Armor can be considered if the enemy team deals almost entirely physical damage.

One Good Spread... can be considered when playing maps where map uptime is critical, e.g. two slow teams on Battlefield of Eternity, or two teams playing a 1-4 split on Braxis Holdout

Level 10

Massive Shove generally provides the best self-peel and playmaking, and can even be used for damage reduction by casting it just before a telegraphed spell would hit (e.g. Pyroblast)

Flailing Swipe can be taken if multiple heroes on the enemy team are diving, especially if they are able to interrupt Massive Shove with their dive.

Level 13

It Hungers makes positioning for good Es easier, and the refund mechanic can make it extremely hard to move in through a Stukov guarding choke points.

Virulent Reaction provides Stukov with an extremely strong CC combo, but is fairly hard to execute on.

Level 20

Top Off provides a nice buff to healing throughput without requiring a change in playstyle.

Push Comes To Shove provides a stronger playmaking tool, and makes getting shoved in a fight extremely punishing.

Controlled Chaos should usually be picked up if Flailing Swipe was necessary for teamfights, as it substantially improves the ability's capability of dealing with diving opponents.