In what ways are taxes unfair to the middle income group than the low income group?

The middle income group is at the place where they do not have to struggle to meet ends meet, but their standard of living is not particularly different from the people from lower income family (low income earning is below $25,000 while middle income earning is above $35,000)

But that's being said, the difference of taxation between middle and lower tax could suprass 10% + additional $ 4,000.

So households in lower end of middle income would fall straight to low income earners after the taxation