The largest angle in a generic triangle does not need to be a right angle.

(eg for an equilateral triangle all angles are 180/3 = 60)

However as above, IF a right angle is one of the angles in a given triangle then it must be the largest angle (as the sum of the 2 remaining angles must be equal to 90, and each angle must be greater than [and not equal to] 0).

Also, it is obviously possible to ha... more

The sum of all three angles in a triangle is 180°. So if the triangle has a right angle then it is the largest angle, as the sum of the other two must be 90°, hence they must be individually smaller than 90°.

A triangle can have an angle larger than 90° though.