I just finished S1 to S4 of Re zero. it did take me a while but every minute of it was definitely worth it.
This is my honest review and opinions.

firstly, there was not a single bad episode, and I mean this because it's very hard to keep me entertained.
Secondly, there wasn't a single badly written character.
All the villains genuinely made me tremble with fear every time they appeared on screen.

Normally with other animes you can sort of predict what will happen next with Re-zero I never ever knew what to expect.

There were so many times when I just stared at the outros like in shock, not knowing where this is heading next.

I still can't choose a favourite character it's too difficult to make that decision.
my favourite seasons are definitely S4 then S3, don't know how we going to wait patiently for the next seasons but I'm here for it all.