My penances are usually too easy, in my opinion. Though, I am very scrupulous and have a tendency to judge myself harsher than my priest.
(He once asked for my suggestion for a penance, and hasn’t done that again! He didn’t take my idea, either…)
The most I have ever been given was to say a decade daily for the rest of my life. (This was a visiting priest, and I only have venial sins. Wonder what he would have given a mortal sinner?!)
My normal confessor’s hardest penance has been 20 decades for one mortal sin against chastity.
However, the last time I confessed I was given one decade and to thank God for His mercy. It was a very appropriate penance, especially with the mercy part. I had been having a hard time with mercy before. I had about 20 mortal sins in 3 days. My priest really helped me to realize God’s infine love and mercy for us.