I know some of the Arians persecuted Catholics cruely but did some Catholics also persecute, torture, and kill some Arians. I heard they did but the person that told me so gave me no details.
I don’t know for sure, but it’s entirely possible. Those were violent times, in general, and the rule of law, as they understood it, was much different from ours today, which we take for granted.
When dealing with things that happened in the distant past, remember that it is unfair to judge people by modern standards. They lived in times and curcumstances, in an environment and under conditions that we have no way of grasping or completely empathizing through the cold lense of history books and comfortable retrospect, centuries removed. A common maxim among historians is that we should not judge those in the past by standards which were unknown to them.
Also, even though it is true that some who have called themselves Christians have, throughout history, acted in an un-Christian manner, that does not render the Christian religion wrong – it only means that the Church contains both saints and sinners, the wheat and the chaff, as Christ predicted. But you do not judge a religion on it’s worst adherents – those who fail to keep it’s precepts – but on it’s best.