I'm not a synthi-expert, but in my cases the synthis sounded whack because they were too clean. They had too good of a tune, they had a too clean soundn and maybe these points will help a little (if you can actually make changes on the presets):
- if there is an "Analog" knob, pull it up to your desire, the analog knob will randomly choose pitch and filter cutoff to a certain amount
- if there are two oszillators, make the one +6 cent and the other -6 cent in tune, it will be veeeeryyy slightly different and gives a little bit of thickness imo
- watch the FM and the Resonance knob. you can mess up the sound depending on what you want to do. if you want some more craziness and some uncontrollable swinging in your sound play with these two buddies
- ADSR of the Amp should be in your desired positions and the ADSR of the filter too, if it is properly adjusted you can man that wah-wah sound on your synthesizer just with the ADSR of the filter
- use effects like distortion, echo/delay, reverb but like a room reverb with a short decay to give a different feeling to it
- layer the synthi with another synth sound and hipass/lowpass/bandpass the best out of everyone to create your own sound
- "Glide"-Knob is useful when you want that 90's gliding westcoast synthi
Hope something works for you, if not, maybe you can show a picture/screenshot of your synthi and his knobs you are using