Strength, or STR, is a stat that determines the attack power of moves.
The STR stat works like this, as quoted by Wikipedia:
The amount of damage of an attack is based on the power of the attacking nanovor and how the actual attack changes the amount of damage done. For example, a nanovor with 100 strength and uses an attack that has damage equal to half its strength will do 50 damage. The damage is always rounded to the nearest whole number.
The higher a Nanovor's strength, the more damage it deals! The lower a Nanovor's strength is, the less damage it deals.
Magnamods are known for having high STR stats. Utilize Magnamods to dent the other team severely!
Velocitrons are known for hacking and mod skills, and many of which can lower the opponent's STR stat, such as Plasma Lash.