What economic system generally taxes the people the highest

If by "taxes people the highest" you mean that more people are paying, or that people are paying more ... I'd say democracy. After all, the government establishes that people are the same and equally matters, in theory, at least.

Following this basic idea, people seem as equals, so they must pay taxes equally, right? What happens with poor people whom can't afford those values? The solution, also inserts in the democratic system, is the isonomy principle, that guarantee equality of citizens treating them according to their necessities.

Following samuel's theory if that is the case wouldn't communism seem a better fit? Communism treats all as equals and that in follow would lead to everyone paying the same amount of taxes.