TOP 5 MORTALS WHO CAN DEFEAT BEERUS:-

5.    V E G E T A 

Yup it is vegeta has been a long Rival of goku and Vegeta is having very high potential as a saiyan though Vegeta didn't got ultra instinct but still if vegeta in rage mode can make himself
so strong that he can go aginst 10% of Beerus's power without whis training then with his super saiyan blue evolution power and with some more training he may defeat Beerus in power. 

4.  B R O L Y

So after Vegeta if there is any mortal it is broly who have a higher chance to defeat lord beerus moreover chances of broly are slightly higher than vegeta as well though in dragon ball super movie goku who experienced only 70% of beerus's power told that broly maybe stronger than even beerus. But still being a legendary super saiyan broly has higher chances of defeating lord beerus.

3.  J I R E N  ( LIMIT BROKEN )

I dont think that i need to tell why i have taken jiren in this list because it is officially mentioned that jiren is stronger than even a god of destruction so by this official statement by whis we can confirm that jiren is stronger or equal to beerus and he could defeat beerus.

2.  G O K U  B L A C K

You must be surprised that why did i include goku black , so basically there are two reasons for that first of all though it is goku's body but goku black is completely a different person and as we saw that goku black used to get immensely strong after each attack that also very quickly even faster than broly 

and all those different tricky powers that goku black posses like creating his many clones who are as strong as him makes him more powerful and so by keeping those points in mind i think i will take goku black in this list as well.

1. M U I   G O K U 

No need to tell that why i included goku and as i am including everyone's most elite power or form. So there is a 99% chance that goku in MUI is stronger than Beerus as MUI goku defeated jiren a mortal who was even stronger than God of destruction of his universe whose power level was roughly equivalent to that of Beerus.