score:8
No, Nixon is not usually considered the worst US president.
Presidential rankings are inherently subjective, and opinions often vary wildly for recent presidents, where they tend to fall along partisan lines. Sometimes opinions are highly convergent; Lincoln is often considered the best whilst the few preceding presidents the worst, all tied to how well they handled the secession and civil war. Nixon, although ranking relatively low, does not appear last.
What stands out about his tenure is the Watergate scandal which represented an unprecedented abuse of power and forced Nixon's resignation, the only US president to do so.