Square wave, playing in the lower octave, with some sexy compression.
That's only a start. It sounds like its layered as well, especially as the track progresses. If I had to take a guess (no expert) I'd say Moog Voyager, or its emulation variants. With some very nice reverb work.
To get a nice bass rumble and growl, layer another osc same octave with the knob turned more towards sawtooth, so you would need continuous waveforms on your synth. Adjust filter appropriately (Moog filter works great). Then turn amp (volume) envelope to low release, high sustain, fast attack. So you get a cut off when the key press is released without a clicking noise.
My meager attempt. I'm no synth expert. But using these settings I got pretty close, minus the compression and delay effect.