all of the new synths we had at my guitar center when i worked there in 05....
romplers (triton, phantom, motif) and some korg, alesis, and novation virtual analogs.
i hate them all...
we did get a couple used items now and again that were great (like a pair of tg77s), but that did not happen very often. U_U
i didn't like the nord lead 2 i bought in 01, or the pulse i bought with it.
i keep on thinking i like viruses, but after i have one of them for a while, i realize i never use it, then i sell it, and then i think about buying one again.
the only soft synth that i really like (other than the soft samplers i use) is sculpture, so i guess i dislike most soft synths.
so....
it's really hard for me to say that there is one "worst synth ever", i hate a lot of them.