Which is correct grammar? "He has already come." or "He has already came"?

He has already come.

Sometimes the insertion of an adjective (in this case "already") makes the verb structure more difficult to see.

If the sentence is re-stated as: ##color(white)("XXX")##He already has come. it is easier to see the perfect tense. (Note that despite its name, the "present perfect" is a action tense).

There are 3 (main, see note below) past tenses (in English):

##{: ("simple past:","independent action completed in past", " | ","He came."), ("present perfect:","action completed before now"," | "," He has come."), ("past perfect:","action completed before some other action in the past"," | ","He had come.") :}##

In addition to these main forms there are also past progressive forms for ongoing actions in the past:

##{: ("simple past progressive"," | ","He was coming."), ("present perfect progressive"," | ","He has been coming."), ("past perfect progressive"," | ","He had been coming") :}##