fullero - cheating, dishonest, deceptive, incompetent, prone to make serious mistakesSpanish example: Marcó los naipes como un jugador fullero.
English example: He marked the cards like a cheating player.
Source: fullero - cheating, dishonest, deceptive, incompetent, prone to make serious mistakes (https://www.123teachme.com/spanish_feeds/word_of_the_day/2021/2/25)