。
That person has strength like a monster.
Literal
That person [topic-は] monster [like-のような] strong-person [copula-だ].
Direct simile using ~のような 'like X.' 化け物 literally 'changed thing' refers to monsters, goblins, or supernatural creatures in folklore; used metaphorically it means 'freak, monstrously powerful being.' 力持ち 'strong person' combines 力 'strength' + 持ち 'holder/possessor,' a productive pattern (金持ち 'rich person,' 家持ち 'homeowner'). The expression is a stock comment on someone's unusual physical strength.