The most natural thing to say would be “Be kind to me.” I would also prefer, for example, “Treat him with kindness” to “Treat him kindly” though both are correct grammatically.

'Act' is an INTRANSITIVE verb so it cannot be followed by a direct object in the manner you suggest. You would need to modify the sentence 'Act kindly to me' for example, with adverb and indirect object.

The word you need is "kindly". He treated me kindly. He acted kindly toward me.

hi. no "act" is an action and its for doing something clear but treat isnt an action its a state of behavior

"act kind to me" sounds a little strange to me. Instead of "treat me kind" it would probably sound more natural to say "treat me kindly"