In an elliptical orbit, the acceleration of an object is highest at the point closest to the body it is orbiting, known as the periapsis or perigee. This is the point in the orbit where the object is nearest to the central mass.
According to Kepler's laws of planetary motion, an object in an elliptical orbit around a central mass experiences a varying gravitational force as it moves through different points in its orbit. The force of gravity is stronger when the object is closer to the central mass and weaker when it is farther away.
Since acceleration is directly proportional to the force acting on an object (according to Newton's second law of motion), the acceleration is highest at the periapsis where the gravitational force is strongest. As the object moves away from the periapsis, towards the apsis or apogee (the farthest point in the orbit), the acceleration decreases since the gravitational force is getting weaker.
So, to summarize, the point in an elliptical orbit where the acceleration is maximum is at the periapsis or perigee, the closest point to the central mass.