Ah, the good old
Dubstep Bass. The fundamental sound is like AshleysBrother said: Two sine waves crushed together with distortion. You can do this with literally any synth that has two oscillators and a waveshaping distortion unit. For this, I used serum.
First step, put two oscillators to sine waves, and set one to be 4 octaves up (serum's limit).
Next step, go get your waveshaper (I used Serum's X-Shaper distortion mode) and make the distortion profile something like this (a.k.a distorting the shit out of it):
As the higher pitched sine wave is being crushed together with the bass frequency one, you're getting that screechy sound. I have two modulation macros set - one that controls the attack time of an envelope I have set to Osc 2's semitone amount, and one that controls the volume mix of the bass level oscillator. Playing around with those two settings and changing one or both of the sine waves to be other square wave based waveforms (squares and triangles and the like) will probably get you every single variation on this sound there is to have. And keep in mind, this works with EVERY synthesizer that has two oscillators, as long as you can distort them to hell and back.
