Which one is regular and irregular verbs john has become or became a rather good actor?

* Become is an irregular verb. Its past tense is became, and its past participle is become.

Here's why:

* Has become is the present perfect tense of the verb "become." It's used to describe an action that started in the past and continues into the present.

* Became is the simple past tense of the verb "become." It's used to describe a completed action in the past.

The sentence "John has become a rather good actor" would be correct if it were describing John's ongoing development as an actor. However, since the sentence is about a specific time in the past (when John became good at acting), "became" is the appropriate verb.