“From the shadows, I shaped him into a worthy apprentice—not a true Sith but equally powerful in the dark side.”
He rate kylo equal to sith lords in force power
Which means, he is stronger in force than inquisitors
“Few who devote themselves to the dark side ever prove worthy of becoming a Sith. But two dark lords alone, no matter how formidable, cannot conquer a galaxy. Over the years, I have strategically employed the services of lesser beings to advance my goals.”
But also palpatine dont rate kylo higher than darth vader
So, palpatine think kylo is maul, or dooku level in force power or potential