To estimate S&P's credit trend for Acciona SA from 2021 to 2022, we will calculate the Adjusted EBITDA, Adjusted Debt, and Funds From Operations (FFO) for both years, and evaluate the year-on-year changes in the Leverage and Cash-Flow Coverage ratios. 

**Step 1: 2021 Adjusted EBITDA**
According to standard S&P methodology, Adjusted EBITDA is calculated by taking Operating Profit (EBIT) and adding back Depreciation & Amortization (D&A), while normalizing for non-recurring or non-cash items (such as impairment reversals and other gains/losses). 
- **Operating Profit (EBIT):** €829m
- **D&A & Provisions** (*Dotacion Amortizacion Y Variacion De Provisiones*): €714m
- **Impairment Reversals** (*Impairment Loss Reversal Of Impairment Loss Recognised In Profit Or Loss*): -€67m (Because the item is stated negatively under expenses, it acts as a reversal/gain that boosted profit. We subtract €67m to normalize).
- **Other Gains/Losses:** -€7m (This reduced profit, so we add back €7m).
*Adjusted EBITDA (2021)* = 829 + 714 - 67 + 7 = **€1,483m**

**Step 2: 2021 FFO**
FFO is calculated as Adjusted EBITDA minus cash interest and cash taxes paid.
- **Cash Interest Paid:** €206m
- **Cash Taxes Paid:** €82m
*FFO (2021)* = 1,483 - 206 - 82 = **€1,195m**

**Step 3: 2021 Adjusted Debt**
We sum all reported short-term and long-term financial debt plus lease liabilities, then deduct eligible cash and cash equivalents.
- **Gross Debt:** €2,364m (Noncurrent bonds) + €2,073m (Noncurrent loans) + €430m (Noncurrent leases) + €1,666m (Current bonds) + €280m (Current loans) + €68m (Current leases) = €6,881m
- **Less Cash & Equivalents:** €2,318m
*Adjusted Debt (2021)* = 6,881 - 2,318 = **€4,563m**

**Step 4: 2021 Credit Metrics**
- **Leverage (Adjusted Debt / Adjusted EBITDA):** 4,563 / 1,483 = **3.08x**
- **Cash-flow Coverage (FFO / Adjusted Debt):** 1,195 / 4,563 = **0.2619** (or 26.19%)

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**Step 5: 2022 Adjusted EBITDA**
- **Operating Profit:** €1,334m
- **D&A & Provisions:** €762m
- **Impairment Reversals:** -€15m (Subtract €15m to normalize the gain).
- **Other Gains/Losses:** €13m (Subtract €13m to normalize the gain).
*Adjusted EBITDA (2022)* = 1,334 + 762 - 15 - 13 = **€2,068m**

**Step 6: 2022 FFO**
- **Cash Interest Paid:** €209m
- **Cash Taxes Paid:** €215m
*FFO (2022)* = 2,068 - 209 - 215 = **€1,644m**

**Step 7: 2022 Adjusted Debt**
- **Gross Debt:** €3,101m (NC bonds) + €2,624m (NC loans) + €439m (NC leases) + €1,139m (C bonds) + €553m (C loans) + €72m (C leases) = €7,928m
- **Less Cash & Equivalents:** €2,360m
*Adjusted Debt (2022)* = 7,928 - 2,360 = **€5,568m**

**Step 8: 2022 Credit Metrics**
- **Leverage (Adjusted Debt / Adjusted EBITDA):** 5,568 / 2,068 = **2.69x**
- **Cash-flow Coverage (FFO / Adjusted Debt):** 1,644 / 5,568 = **0.2953** (or 29.53%)

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**Step 9: Trend Evaluation**
- **Signal 1 (Leverage):** 2.69x - 3.08x = **-0.39x**. This translates to a decrease of more than -0.2x, firmly indicating an **Improving** trend.
- **Signal 2 (Cash-flow coverage):** 0.2953 - 0.2619 = **+0.0334** (+3.34 percentage points). This is greater than the +0.03 threshold, which also indicates an **Improving** trend.

Because both core ratios exceed the specific S&P momentum thresholds for improvement, the comprehensive credit trend year-over-year is evaluated as Improving.

<answer>Improving</answer>