Do you have a feature for a customer wise discount?
Suppose a customer A logged on the website and see all the product 10% discount and another customer B logged on the website and see all the product 20% discount.

Maybe tier prices assigned to customer roles will be enough for you? Just assign customer to specified customer role and then assign tier prices to that roles. Tier prices can be configured in the admin panel, go to Products -> edit desired product and go to "Prices" tab, scroll down and you will see the Tier prices section. It should meet your requirements. If you need more sophisticated solution, our developers can create some customization for you.

Hi,
I was thinking in percentage right now it is a fixed price at tier pricing. Thank I will try to develop a plugin that will use a promotion discount at price tier.

Product level discounts are good. Category level tier discounts might be another good avenue to explore.