Dr. Crime is the costumed identity of Edward Elmgren, a villain in Marvel’s main universe, Earth-616. Elmgren’s primary weapon was a blow gun that fired darts coated with a lethal poison. In 1941, Elmgren led an expedition into the Amazon looking to find riches, but instead found a concentrated shrinking formula used by an Amazonian tribe to shrink heads. This shrinking formula enabled Elmgren to reduce the size of human beings and their clothes. As Dr. Crime he began administering this liquid using a water pistol. During a battle with Captain America and Bucky, Elmgren attempted to escape by using his own shrinking formula, but was swooped up by a passing eagle and likely carried to his death.
Note: Dr. Crime is probably “the best villain name/villain costume combo of all time.”