Question Cpu using 100% in games and cpu is only 50-60%

Assassin's creed odessy , valorant , fortnite
I play Assassins Creed Odyssey, that will max out a 4 core/4 thread CPU. There's not an awful lot you can do about it but turning down settings like Volumetric Clouds can help reduce the CPU load if you have those enabled. An i5 7400 is not going to run this game at a constant 60 FPS though. I don't play the other games so can't really comment, but really 4 core's/4 threads has reached it's limit in modern gaming.
 
When your CPU is running at 100% while your GPU is only at 50-60%, it means that the CPU is bottlenecking the GPU. In other words, the CPU is not able to keep up with the demands of the GPU, which is causing the GPU to not reach its full potential.
In your case, the i5-7400 is a quad-core CPU with a base clock of 3.0 GHz and a boost clock of 3.5 GHz. While it may have been a capable CPU when it was released, it may struggle to keep up with modern games that demand more cores and higher clock speeds.
To improve your gaming performance, you may want to consider upgrading your CPU to a newer model with more cores and a higher clock speed. This would allow your CPU to better keep up with your GPU and prevent it from bottlenecking.
In addition to upgrading your CPU, you may also want to consider upgrading your RAM to 16GB, as some modern games can be quite demanding on memory.
Lastly, make sure that your graphics card drivers are up to date and that your power settings are optimized for gaming performance. You may also want to check that your game settings are optimized for performance rather than visual quality.