I would say that the most minimal language that is still used today will be lambda calculus , but I seriously doubt that it can be called a programming language. LISP is a family, and Python is one of the most widely used languages with less instructions. If you use expert systems, CLIPS is also used for research and development of games. and it contains very few instructions (it is based on logic)
Here you have some more answers.
What is the smallest functional programming language?