Final answer:
Lady Macbeth is the character in 'Macbeth' who speaks of wanting her blood to be thick and to block remorse.
Step-by-step explanation:
The character who speaks of wanting their blood to be thick and to block remorse in "Macbeth" is Lady Macbeth. In Act 1, Scene 5, Lady Macbeth calls on the spirits to "unsex" her and make her blood thick, so she can carry out the murderous deeds without feeling guilty or remorseful. She asks the spirits to stop up the access and passage to remorse, so that no compunctious visitings of nature can shake her purpose. This desire for thick blood symbolizes Lady Macbeth's ruthless determination and her willingness to do whatever it takes to achieve her ambitions.