Unlike the fantasy RPG it evolved from, which has feats only members of the fighter class can take, Starfinder does not have feats that only Soldiers can take. It does have fighting styles and gear boosts as exclusive class features, but those serve somewhat different roles. As a class that is supposed to be the master of standard combat, it still makes sense that soldiers be able to use their bonus combat feats to pick up specific feats that allow them to perform actions in combat other classes cannot master. Here are some possible examples of soldier combat feats.

Soldier Bonus Feats: These feats can only be taken using the soldier’s bonus combat feat class feature. A soldier must meet the feat’s prerequisites, but also cannot take them with feats gained from other sources–only their bonus feats gained from the soldier class.

BRACE (Combat, Soldier Bonus)
You have learned how to set yourself before an attack, trading defense for accuracy.
Prerequisites: Soldier Level 2.
Benefit: At the beginning of your turn, before you take any other actions, you can choose to brace as a move action. You gain a +2 bonus to attack rolls, and take a -4 penalty to your EAC and KAC. This penalty does not apply to your AC values against combat maneuvers, and it lasts as long as you are braced and until the beginning of your next turn even if your brace ends. You remain braced until you move, or choose to end your brace as part of any other action (which ends the brace after the action you combine it with).

IMPROVED FIRE SUPPORT (Combat, Soldier Bonus)
You know how to fire for effect.
Prerequisites: Soldier Level 2.
Benefit: You you provide covering fire or harrying fire (including when you do so while using other abilities, such as Suppressive Fire), until the beginning of your next turn the bonuses apply to all attacks against the ally you protect with covering fire or attacks allies make against the foe you penalize with covering fire.
Additionally if you take a full attack, you can use one or both of those attacks to perform covering fire or harrying fire (taking the normal attack penalty for your full attack to the attack roll needed for the covering or harrying fire to be successful).

OVERWATCH (Combat, Soldier Bonus)
You are skilled at attacking when specific circumstances arrive.
Prerequisites: Soldier level 6.
Benefit: You can ready an action to enter overwatch. While in overwatch, until the beginning of your next turn you can make an attack as a reaction to any action by others that you perceive. Your attack always occurs after the triggering action, you you do not need to declare what that circumstance is in advance. If you are knocked down or moved, your overwatch ends.

OVERWATCH MASTERY (Combat, Soldier Bonus)
You are expert at attacking when specific circumstances arrive.
Prerequisites: Overwatch, soldier level 8.
Benefit: When you are in overwatch, you can choose to take a -4 penalty to the first attack you make as part of overwatch. If you do so, you can make a second overwatch attack (also at -4) before the beginning of your next turn.

SKIRMISH (Combat, Soldier Bonus)
You can move up quickly to engage foes in melee and move swiftly from target to target.
Prerequisites: Soldier level 4.
Benefit: When you make a full attack with melee attacks, you can move up to your speed. You can move before or after both attacks, but all your movement must be taken at once, and you cannot move between the attacks. Once you make a melee attack roll against a foe while using Skirmish, until the beginning of your next turn your movement does not provoke attacks of opportunity from that foe.
Special: If you also have Spring Attack, when you use Skirmish you can break up your movement to move before, between, and after the attacks as long as your total movement does not exceed your speed.

WALKING FIRE (Combat, Soldier Bonus)
You can move while laying down heavy fire.
Prerequisites: Soldier level 4.
Benefit: When you make a full attack with ranged attacks, you can move up to your speed. You can move before or after both attacks, but all your movement must be taken at once, and you cannot move between the attacks.
Special: If you also have Shot on the Run, when you use Walking Fire you can break up your movement to move before, between, and after the attacks as long as your total movement does not exceed your speed.

Patreon
I have a Patreon. It supports the time I take to do all my blog posts, but especially longer and more experimental ones like this. If you’d like to see more game-bending rule options (or more fiction, game industry essays, game design articles, worldbuilding tips, whatever!), try joining for just a few bucks and month and letting me know!