If you want an attack to feel strong, a frame freeze is not enough. Practice attack animation phases: anticipation, attack, recovery. A nice impact is about properly timing all three.
Anticipation is usually short - a couple of frames, that show the windup motion.
Attack can honestly be just one smeared frame. The less time it takes, the harder the hit feels.
Recovery - it's the longest one. Make sure the inertia from that attack is conveyed well. Make the character look like they struggle a bit to recover balance or something that shows that they actually applied force.
Those are fundamentals, get them right first. Freeze frames, screen shakes - those are the seasoning, not the main dish here.