Delusional

google

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late Middle English (in the sense ‘act of deluding or of being deluded’): from late Latin delusio(n- ), from the verb deludere (see delude).

wiktionary

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delusion +‎  -al

etymonline

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delusional (adj.)

"pertaining to or of the nature of delusion; afflicted with delusions," 1858, from delusion + -al (1).