worst opening starting with d

Danish Gambit

Doggy gambit

Disrespect Gambit

de cow

duras gambit no question

Damiano Defense---even the name lets you know. Why stop there? Go full-on Ooga-Booga and follow it up with the Damiano Gambit.

Ladies and Gentlemen, Boys and Girls, dying time's here!

Which Damiano?

1.e4 e5 2.Nf3 f6 sucks.

1.e4 e5 2.Nf3 Nf6 3.Nxe5 Nxe4 is actually legit!

Thriller,given that the name of this thread is "Worst Openings beginning with the letter D" don't you think that we are talking about the mighty

Damiano Defense (and Damiano Gambit, if desired)

1.e4 e5

2.Nf3 f6

3. Nxe5 fxe5

The second line you list ISN'T the Damiano, it's the Classical Petrov's Defense, Damiano line. As you say it is legit, but a tougher line to play for black. hence that's why it isn't called "the main line".

As an aside, The Damiano Defense is easily worse than the Duras Gambit. Black can win with either, but it's easier with the Duras (though both are more likely to lead to the black pit of despair)