What is a noun for "one who is responsible"?

Solution 1:

I would just say "responsible person." Where I work, we assign tasks to the appropriate person for each item in any of our action lists. That person becomes the "responsible person."

Solution 2:

Well sometimes I used Person in Charge (PIC) in some of my school events, I think it's even suited in the workplace.

Edit:

The Person-in-Charge (PIC)

In any food establishment will often be the person who has the overall responsibility for running that Location during the entire time of operation. If there are multiple shifts, the PIC will be responsible for the proper functioning of the food establishment’s operation during the work shift.

The PIC can be the owner of the business or a designated person, such as a shift leader, chef, kitchen manager or similar individual who is always present in the work site and has direct authority, control or supervision over employees who engage in the storage, preparation, display or service of foods. The PIC is accountable to their employer and the government for making sure that they and the employees on their shift are following established policies and procedures for food safety. - Foodsafe.ae

Solution 3:

What do you think about assignee?