To determine the extent to which ENI S.p.A. should utilize hybrid bonds relative to S&P Global Ratings' equity credit cap, we follow S&P's methodology for corporate hybrids:

1.  **Calculate Total Adjusted Capital:** This is defined as Total Debt plus Total Equity.
    *   **Total Equity:** From the balance sheet at 2023-01-01, "Equity" = €55,230,000,000.
    *   **Total Debt:** We sum the reported borrowings. 
        *   "Shortterm Borrowings" = €4,446,000,000
        *   "Current Portion Of Longterm Borrowings" = €3,097,000,000
        *   "Longterm Borrowings" = €19,374,000,000
        *   Total Debt = €4,446,000,000 + €3,097,000,000 + €19,374,000,000 = €26,917,000,000.
    *   **Total Adjusted Capital** = €26,917,000,000 + €55,230,000,000 = €82,147,000,000.

2.  **Calculate the 15% Equity Credit Cap:**
    *   15% of Total Adjusted Capital = 15% × €82,147,000,000 = €12,322,050,000.

3.  **Determine Current Outstanding Hybrids:**
    *   ENI has outstanding perpetual subordinated bonds, which are classified as equity under "Increase Decrease Through Net Issue Reimbursement Of Perpetual Subordinated Bonds Equity" and "Decrease Through Coupon Payment On Perpetual Subordinated Bonds Equity". 
    *   To find the balance, we look at the equity roll-forward. The "Other Reserves Member" shows the movements for these bonds: a €2,000,000,000 issuance in 2021 and a €3,000,000,000 issuance in 2020.
    *   There are no redemptions reported for 2022. Thus, the total outstanding perpetual subordinated bonds (hybrids) = €5,000,000,000.

4.  **Assess Remaining Capacity and Utilization Extent:**
    *   The maximum allowable hybrids under S&P's 15% cap is €12,322,050,000.
    *   ENI's current hybrid usage is €5,000,000,000.
    *   Remaining capacity = €12,322,050,000 - €5,000,000,000 = €7,322,050,000.
    *   Since ENI has significant remaining capacity (it has used less than half of its cap), it can and should utilize hybrid bonds further to optimize its cost of capital and maintain its strong investment-grade credit profile. S&P allows up to 100% of the cap, and because the cap is not breached or near its limit (currently at ~40.7% of the cap), the company should utilize the full extent of the allowed cap (100% of the cap limit) if it desires to maximize the financial flexibility and tax shielding benefits of hybrids without jeopardizing its rating. 

<answer>100%</answer>