smell blood

blood and guts

Gore; gruesome images.

blood in the water

In a competitive situation, the exhibition of apparent weakness or vulnerability by one party, especially when this leads to a feeling of vulnerability or greater pressure to perform on the part of the weak party, or enhanced expectation of victory by the others.

blood is thicker than water

Family relations and loyalties are stronger than relationships with people who are not family members.

blood, sweat and tears

A person's determination and hard work.

get blood out of a stone

To do something difficult, frustrating, or pointless.

have blood on one's hands

To be responsible for a violent act.

have someone's blood on one's head

To be responsible for someone's death, pain, or misfortune.

make someone's blood boil

To cause a person to feel angry or very annoyed, especially in situation in which one cannot fully display that feeling to others.