He was a fine villian and it was a fine season - in my view.
However he was also a fairly poorly designed character from a world narrative prespective.
Effectively he was merely given his abilities (and more importantly his proficency) due to rule of cool - which nobody else in the series (or the previous series) benefits from, yes they unlock powers but only after already effectively being highly proficent beforehand and struggling to gain that proficiency, Zaheer just gets given what he needs to be a rival to anyone he faces without any real work or time on his part to acheive such.