The earliest text here has the third person singular verb form has. Joseph Smith, in his editing for the 1837 edition, thought to change the has to have, probably because of the immediately preceding plural abominations. But the actual subject is the singular scene, so the emendation to the plural have was ignored by the time the 1837 edition was typeset. Subsequent editions have continued with the singular has, as will the critical text.
Summary: Maintain the singular verb form has in Mormon 2:18, the earliest reading; the subject for has is the singular noun scene.