Mixing:
Pitch corrections (right amount of Auto-tune effect plugin if compulsory)
Equalizer (EQ)
Compressor
De-Esser ( reductions of sibilance sounds )
Multi-band compression
Stereo panning
Level balancing
Automation (in terms of volume, effects sends, etc.)
Audio repair
Reverb, Delay and other effects
Mastering:
Dynamic EQ (if compulsory )
Multi-band compression (if compulsory)
Saturation (if compulsory)
Stereo widening a mix with MS Processing (if compulsory)
Maximizing the loudness of the final mix (most important)