I traverse along the pathway of darkness and imagination… Entering the realm born by human imaginations… Challenging Harry Potter’s magic, commanding the great Pirates of the Caribbean Terminating the Terminator’s strength, tearing apart the Matrix’s Hallucination Virus is my slave Endurance my inheritance Growing and hunting in the boundless universe Breaking through boundaries in a mysterious space Desiring evil, conspiracy and betrayer. Who can redeem what was already lost In a battle of demons who can leave an immortal legacy A declining Trump card, Ultimate evolution! I’m… on a journey! We are one!
Because Jones was extremely wary of the power of the MIB's energy weapons, he had expended a lot of effort to mutate his exoskeleton to make him almost immune to those weapons. However, it came at a great cost.
To explain it in simple terms, let's assume the Jones that had evolved to his peak form had 100 points of life energy. If he'd followed his previous direction of evolution, he'd only need to spend 10 points of life energy on his carapace. The remaining 90 points of life energy could be used to strengthen other aspects of himself.
However, to evolve a carapace that was immune to energy weapons consumed 60 points of life energy. He only had 40 life energy remaining to assign to attack, speed, HP and agility. His all-round attributes naturally took a big hit.
And of course, Jones' resistance to firearm-type physical weapons had also weakened a considerable extent!