"you are most kind"（你真是太好了） usually express thanks to other person, but "you are really good"（你真的很棒）mostly use when you think a man well on something.

I think "You are most kind' means " 你真善良。”It express the warm heart of a preson. If you want to say;"你真好。”Ｙou can say:" You are really very kind."

kind ：in here : 友好

i think "仁慈" is mostly used for old people being kind to young people. in casual conversation, you could just say "谢谢你，你人真好"/"谢谢你，你真好"

1.亲切的, 和蔼的, 友好的, 仁慈的 The kind old man is accompanied all the time. 这位和蔼的老人一直有人陪伴着。 He is kind and friendly despite his rather bluff manner. 他为人厚道, 待人亲切, 虽然态度有点粗鲁。 She was kind and generous. 她心地善良, 宽容大量。 They were exceedingly kind. 他们极为客气。 She has been very kind about letting us use her house. 她十分友好, 让我们使用她的房子。 Be kind to animals. 对动物要仁慈。 Be kind to old people. 对老人要爱戴。 She is always kind to her pupils. 她对她的学生总是很和善。 He is kind and gentle to the weak. 他对弱者总是友好和善。 He is kind with his parents. 他和他的双亲关系很好。 You are kind to come. 难得你来。 You were kind enough to wait for us. 你等我们, 真是太好了。 It's very kind of you to show so much concern for us. 谢谢您对我们这么关心。 It was very kind of you to visit me when I was ill. 感谢你在我生病时来看我。 It's too kind of you to have told me that. 你把那件事告诉了我, 真是太好了。 2.富于同情心的 3.心胸宽广的，宽宏大量的，宽容的 4.诚挚的，衷心的，恳切的 5.[口语]令人感激的；体贴的 6.(天气)温和的，宜人的