Full settlement is not including my variable pay

I worked for a tyrant. Started in Jan 2018 and quit in Aug 2018. I had a basic salary which was split in three. A basic given to me monthly, a part of the salary was given on quarterly basis as a variable pay and another vairable pay to be given to me at as annual which was also counted monthly.
Now I�ve quit and when I asked for the rest of variable pay which was mentioned in my contract the ex boss says he won�t as it supposed to be give at the end of the year and I didn�t not complete it and also the one part of my quarterly pay also is pending which he says I am not eligible for it
How far is he right ? Can I take any legal action against him ? Please advise as the amount is fairly good and I wouldn�t want to walk away from what is right fullly mine