Superlative of Alone

Hi there


I wrote a sentence in a book and I wasn't sure if it was right or even if it exists, please what is the superlative of the word "alone"? I wrote : "Day by day he felt more alone", but I tried to find the answer online and I couldn't, there was one website that mentioned it as correct, other said that "alone" doesn't have superlative so I got confused.

I'd appreciate your help

thanks

Raquel