noun which may take the genitive case particle 'no'
bloodstained; covered in blood
Describes a person, object, or surface that is smeared or drenched with blood. Often used in violent or accident contexts.
事故現場には血まみれの服が落ちていた。
Bloodstained clothes were lying at the accident scene.
彼は血まみれになって病院に運ばれた。
He was taken to the hospital covered in blood.
血だらけ also means 'covered in blood', but だらけ often implies a messy, undesirable state over a wide area, while まみれ emphasizes being smeared or drenched with a substance.
Compound of 血 (chi, 'blood') and まみれ (mamire, 'smeared with'), the continuative form of the verb まみれる (mamireru, 'to be smeared').