Characterization is an important tool to define how a character thinks and how they can or can`t be outsmarted. here are some factors:
1- A character`s inteligence: The most obvious step is to establish how smart is the character. If the enemy is an idiot, outgambiting him would be easy, for smarter foes, it would get trickier.
2- Emotional, psychological factors: Also, there are psychological factors. Even a clever foe can behave foolishly due to emotional reasons. Ex: hurting an arrogant`s ego can make them renounce to an advantageous position to prove themselves (think about the classic villain who throws away his gun to go into a fistfight with the protagonist), or provoking a hot tempered enemy and using his rage to lure him into a trap.
3-Preparation and knowledge: Another factor is how much do a character knows about his enemy? even a clever fighter may struggle if their enemy keeps him guessing.,If a fighter knows about his oponents abilities, strenghts and weakesses, he has a tactical advantage. A smart fighter will try to keep his abilities a secret, or make it look like his powers work differently to mislead his opponent.
Some may have reasons to show off their powers aside from ego or flashyness. They may be attempting to intimidate their foes into submission, or agreed to show their powers to have an honorable fight or maybe they trust their team members enough to make sure they know about his capabilities to make a solid attack plan.
4-Teamwork, communication and coordination: Some groups work better together than others. Communication can be key in teamfights and contests. A cunning strategist may try to exploit the inner struggles of an oposed team for their own advantage.
5-Adaptation skills: how well do this strategist adapts when things go outside of their plan?, some may be able to adapt quickly when they realize what is going on. Others may be too overwhelmed by this turn of events.
6-Leadership, people skills and manipulation: you don`t need to be strong if you can get strong people on your side, or if you can just trick your foes into pitting against each other. (being able to put a fight or escape if they realize the ruse is important too) Not everyone leads by instilling fear. Some are inspiring paragons of their teams, others can keep the calm in times of adversity
7-Reputation: if a character backstaves a lot, others will begin to realize it and not trust them, if a living legend is saying an inspiring speech to keep fighting, it will be way more effective than if a random soldier that joined last week says it.
Those are the ones that came to mind for now, hope this helps!
edit: just remembered a couple of books to recommend about strategy in any kind of conflicts:
"the 36 chinesse strategies" and "the art of war"