an example of pool, careless work

blunder

to make (something) difficult to do or understand

confuse, make difficult

to make (something) dirty, impure or diseased (by touching or adding something impure)

adulterate

to make (a region, water; a person's thoughts etc) dirty or impure

corrupt, violate

to cause (a discussion, speech, flow of something etc) to be stopped or be in a state of disorder

upset, disorganize

to make (something) useless or unsatisfactory; to harm (a child's personality) by too much kindness or lack of discipline

ruin, hurt