Looks like you are looking for the antagonistic pair. The muscular group that flexes the arm would be the antagonistic pair of tricep brachi and the brachialis.
The brachialis is a muscle in the upper arm that flexes the elbow joint.
which shoulder muscle allows you to adduct your arm
The main muscle that flexes the forearm is the biceps brachii.
Palmaris Longus
The muscle that flexes and adducts the arm at the shoulder, working alongside the pectoralis major, is the latissimus dorsi.
Pectoralis major
When the biceps muscle contracts and shortens, it primarily flexes the elbow, bringing the forearm closer to the upper arm. In this action, the triceps muscle relaxes and lengthens to allow for smooth movement, acting as an antagonist to the biceps. This coordinated action helps maintain balance and control during arm movements.
A muscle which bends or flexes any part; as, the flexors of the arm or the hand; -- opposed to extensor.
-Flexion of the Arm -Flexion of the Forearm-Supination of the Forearm-Stabilization of the glenohumeral joint
break throw muscle shrug write
The teres major muscle is considered to be antagonistic to the teres minor muscle. The teres major muscle is a larger muscle located in the upper arm that works to extend, medially rotate, and adduct the arm, while the teres minor muscle is a smaller muscle that works to laterally rotate the arm.
The brachialis is a muscle in the upper arm that flexes the elbow joint, allowing you to bend your arm. It lies underneath the biceps brachii muscle and is important for movements like lifting and carrying objects.