The OP defined "worst Hokage" as a politician/ruler, not a ninja so combat expertise does not count.
I'm not saying the 3rd is the worst, because it's simply unfair for him. The other Hokages' ruling style save for the 5th and the 3rd weren't detailed as much nor the situation of the village during their time (we were only given bits and pieces of info). However, people have been crediting the 3rd for his heroism against Orochimaru and put it in the same pedestal as the 1st, 2nd, and 4ths. They seem to forget that he was the one who failed to put an end to Orochimaru in the first place, due to emotional weakness (even his summon companion pointed it out), which directly contradicts with his role as the Hokage. Since then, all lives taken by Orochimaru can be indirectly blamed on his failure.
Again, we don't know the whole history. We shouldn't be judging who's the worst ruler. It's only immature to do so.
I'm not saying the 3rd is the worst, because it's simply unfair for him. The other Hokages' ruling style save for the 5th and the 3rd weren't detailed as much nor the situation of the village during their time (we were only given bits and pieces of info). However, people have been crediting the 3rd for his heroism against Orochimaru and put it in the same pedestal as the 1st, 2nd, and 4ths. They seem to forget that he was the one who failed to put an end to Orochimaru in the first place, due to emotional weakness (even his summon companion pointed it out), which directly contradicts with his role as the Hokage. Since then, all lives taken by Orochimaru can be indirectly blamed on his failure.
Again, we don't know the whole history. We shouldn't be judging who's the worst ruler. It's only immature to do so.