**Step 1: Identify the relevant industry**
REDEIA CORPORACION SA (Red Eléctrica Corporación) is the primary transmission system operator and electricity transporter in Spain. According to the provided S&P methodologies, this aligns perfectly with the **Regulated Utilities** sector (specifically "Electricity National industry and utilities"). 

**Step 2: Estimate 2021 Adjusted_EBITDA**
For Regulated Utilities, EBITDA margin is typically used for profitability, and we use the standard baseline formula. 
- Reported Profit Loss (2021): 686,284,000 EUR
- Depreciation And Amortisation Expense (2021): 522,114,000 EUR
- Reported EBITDA = Profit Loss + Depreciation & Amortisation = 686,284,000 + 522,114,000 = 1,208,398,000 EUR
- No specific lease, pension, or JV proportional adjustments are indicated in the data (equity method profits are already reflected in the P&L). 
- **2021 Adjusted_EBITDA = 1,208,398,000 EUR**

**Step 3: Estimate 2021 FFO**
For Regulated Utilities, FFO = Adjusted EBITDA - Cash Interest - Cash Taxes.
- Adjusted EBITDA = 1,208,398,000 EUR
- Cash Interest (Finance Costs for 2021, assuming cash=accrued): 115,453,000 EUR
- Cash Taxes (Income Tax Expense for 2021): 201,793,000 EUR
- **2021 FFO = 1,208,398,000 - 115,453,000 - 201,793,000 = 891,152,000 EUR**

**Step 4: Estimate 2021 Adjusted_Debt**
Using the baseline formula: Adjusted_Debt = Reported Debt + Leases + Pension Deficit + Guarantees + Hybrid Debt + Other Debt-like Items - Eligible Cash.
- Reported Debt (Longterm Borrowings + Current Borrowings): 589,617,000 + 1,391,722,000 = 2,281,339,000 EUR
- Eligible Cash (Cash And Cash Equivalents): 1,574,427,000 EUR
- We exclude "Other Noncurrent/Current Financial Liabilities" (derivatives, payables) as they are not debt-like borrowings.
- **2021 Adjusted_Debt = 2,281,339,000 - 1,574,427,000 = 706,912,000 EUR**

**Step 5: Calculate 2021 Adjusted_Debt / Adjusted_EBITDA**
- Ratio = 706,912,000 / 1,208,398,000 = 0.585x

**Step 6: Calculate 2021 FFO / Adjusted_Debt**
- Ratio = 891,152,000 / 706,912,000 = 1.261 (or 126.1%)

**Step 7: Estimate 2022 Adjusted_EBITDA**
- Reported Profit Loss (2022): 681,187,000 EUR
- Depreciation And Amortisation Expense (2022): 544,992,000 EUR
- Reported EBITDA = 681,187,000 + 544,992,000 = 1,226,179,000 EUR
- **2022 Adjusted_EBITDA = 1,226,179,000 EUR**

**Step 8: Estimate 2022 FFO**
- Adjusted EBITDA = 1,226,179,000 EUR
- Cash Interest (Finance Costs for 2022): 116,468,000 EUR
- Cash Taxes (Income Tax Expense for 2022): 188,330,000 EUR
- **2022 FFO = 1,226,179,000 - 116,468,000 - 188,330,000 = 921,381,000 EUR**

**Step 9: Estimate 2022 Adjusted_Debt**
- Reported Debt (Longterm Borrowings + Current Borrowings): 5,491,124,000 + 721,845,000 = 6,212,969,000 EUR
- Eligible Cash (Cash And Cash Equivalents): 794,824,000 EUR
- **2022 Adjusted_Debt = 6,212,969,000 - 794,824,000 = 5,418,145,000 EUR**

**Step 10: Calculate 2022 Adjusted_Debt / Adjusted_EBITDA**
- Ratio = 5,418,145,000 / 1,226,179,000 = 4.42x

**Step 11: Calculate 2022 FFO / Adjusted_Debt**
- Ratio = 921,381,000 / 5,418,145,000 = 0.170 (or 17.0%)

**Step 12: Classify the year-on-year credit trend**
- **Signal 1 (Leverage):** Change in Adjusted_Debt / Adjusted_EBITDA = 4.42x - 0.585x = +3.835x. This is ≥ +0.2x, indicating **Deteriorating**. (The massive increase is driven by current borrowings being reclassified to non-current in 2022 and the significant drop in eligible cash).
- **Signal 2 (Cash-flow coverage):** Change in FFO / Adjusted_Debt = 0.170 - 1.261 = -1.091. This is ≤ -0.03, indicating **Deteriorating**.

Since both signals agree, the trend is clearly Deteriorating.

<answer>Deteriorating</answer>