What's the worst major party in the world?

[I spent the winter writing songs about getting better]

We'll define "major" as say, oh getting at least 5% of the vote and able to get at least a double digit number of seats in their respective country's legislature.

I'll have to go with either Golden Dawn or one of those really awful Israeli parties.

[I spent the winter writing songs about getting better]

Though speaking of which, are there any unreformed Stalinist parties that hold seats won in free and fair elections?

Communist Party of Greece, though they are too hilarious to not love.

[I spent the winter writing songs about getting better]

I admit I'm unfamiliar with what makes the BJP so horrible.

Hindu nationalist extremists. They're the part of who like to stir up tensions and violence toward Muslims (think Slumdog Millionaire), engage in violence against missionaries and want to ban conversion.

[I spent the winter writing songs about getting better]

Zimbabwe is not "democratic" by any remotely meaningful definition of the word, unless you actually believe the ZANU-PF has governed for over 30 years because the voters just like them and their record that much. Might also want to refer to Freedom House.