It’s not primarily the physical suffering by which Christ demonstrates his love for us, but the spiritual, mental, and emotional weight of what he endured.
The pain of betrayal from those closest to Him, the very crowd who laid palm branches before Him now begging for His blood, the ultimate sacrifice for people He loves who ignorantly and arrogantly hate Him, and the feeling of being momentarily ‘forsaken’ by His Father.
Not to make a trite comparison, but Tolkien said that Bilbo conquered the dragon before coming face to face with him, the moment he chose to go on through the dark passage despite his fears.
In the same way, Jesus conquered sin and death before the Cross, the moment in Gethsemane when sweating blood and crying out for God to take the cup from him, chose not His own will, but that of the Father.