From my learning I agree with 2Code (-2

^{2} = -4), although I've certainly come across the opposite perspective where a negative sign alone preceding a number is taken to be part of the number, not an operator. That's what causes the confusion/difference. It should always be treated as an operator (written as just - instead of -1* for short).

Qalculate gives the correct answer of -4; it even helpfully expands it as: -2^2 = -(2^2) = -4.

Excel gives an incorrect answer of 4 for -2^2. MS is aware of this... their answer is basically that Excel is for accountants, not mathematicians

Parentheses are our friends