Step 1: Identify the relevant industry
REN - Redes Energéticas Nacionais, SGPS, S.A. is a Portuguese energy networks operator (electricity and gas transmission). Based on the provided industry methodologies, it falls under the "Regulated Utilities" sector, specifically the "Electricity National industry and utilities" and "Gas National industry and utilities" subsectors. 

Step 2: Estimate 2021 Adjusted_EBITDA
For Regulated Utilities, EBITDA is generally calculated as Operating Income + Depreciation and Amortization. 
- Operating Income (Profit Loss From Operating Activities) 2021: 218,863,000 EUR
- Depreciation And Amortisation Expense 2021: 241,940,000 EUR
Adjusted_EBITDA 2021 = 218,863,000 + 241,940,000 = 460,803,000 EUR

Step 3: Estimate 2021 FFO
For Regulated Utilities, FFO = Adjusted EBITDA - Cash Interest - Cash Taxes.
- Cash Interest (Finance Costs) 2021: 54,356,000 EUR
- Cash Taxes (Income Tax Expense Continuing Operations + Energy Sector Extraordinary Contribution) 2021: 52,081,000 + 27,041,000 = 79,122,000 EUR
FFO 2021 = 460,803,000 - 54,356,000 - 79,122,000 = 327,325,000 EUR

Step 4: Estimate 2021 Adjusted_Debt
Adjusted Debt = Reported Debt + Leases + Other debt-like items - Eligible Cash.
- Reported Debt (Longterm Borrowings + Current Borrowings) 2021: 2,390,852,000 + 375,221,000 = 2,766,073,000 EUR
- Leases (Trade And Other Non Current Payables + Trade And Other Payables Current approx, though typically recognized as lease liabilities; we use the standard reported debt aggregates): We rely on the reported borrowings as the primary debt metric. Given no specific lease figures, we use the borrowing lines. 
- Eligible Cash (Cash And Cash Equivalents) 2021: 398,759,000 EUR
Adjusted_Debt 2021 = 2,766,073,000 - 398,759,000 = 2,367,314,000 EUR

Step 5: Calculate 2021 Adjusted_Debt / Adjusted_EBITDA
Ratio 2021 = 2,367,314,000 / 460,803,000 = 5.14x

Step 6: Calculate 2021 FFO / Adjusted_Debt
Ratio 2021 = 327,325,000 / 2,367,314,000 = 13.83% (or 0.1383)

Step 7: Estimate 2022 Adjusted_EBITDA
- Operating Income (Profit Loss From Operating Activities) 2022: 239,721,000 EUR
- Depreciation And Amortisation Expense 2022: 249,276,000 EUR
Adjusted_EBITDA 2022 = 239,721,000 + 249,276,000 = 488,997,000 EUR

Step 8: Estimate 2022 FFO
- Cash Interest (Finance Costs) 2022: 67,394,000 EUR
- Cash Taxes (Income Tax Expense Continuing Operations + Energy Sector Extraordinary Contribution) 2022: 54,263,000 + 28,019,000 = 82,282,000 EUR
FFO 2022 = 488,997,000 - 67,394,000 - 82,282,000 = 339,321,000 EUR

Step 9: Estimate 2022 Adjusted_Debt
- Reported Debt (Longterm Borrowings + Current Borrowings) 2022: 1,695,362,000 + 638,944,000 = 2,334,306,000 EUR
Note: The 2022 balance sheet shows a 1,000,000,000 EUR asset and liability related to the "Transitional Gas Price Stabilization Regime Decree Law84D2022". This is a regulatory pass-through mechanism, not genuine corporate debt, so it is excluded from Adjusted Debt.
- Eligible Cash (Cash And Cash Equivalents) 2022: 365,292,000 EUR
Adjusted_Debt 2022 = 2,334,306,000 - 365,292,000 = 1,969,014,000 EUR

Step 10: Calculate 2022 Adjusted_Debt / Adjusted_EBITDA
Ratio 2022 = 1,969,014,000 / 488,997,000 = 4.03x

Step 11: Calculate 2022 FFO / Adjusted_Debt
Ratio 2022 = 339,321,000 / 1,969,014,000 = 17.23% (or 0.1723)

Step 12: Classify the year-on-year credit trend
Signal 1 (Leverage): Change in Adjusted_Debt / Adjusted_EBITDA = 4.03x - 5.14x = -1.11x. 
This is ≤ -0.2x, so Signal 1 is Improving.

Signal 2 (Cash-flow coverage): Change in FFO / Adjusted_Debt = 0.1723 - 0.1383 = +0.034 (or +3.4 percentage points). 
This is ≥ +0.03, so Signal 2 is Improving.

Both signals agree, indicating an Improving trend. The massive decline in net debt and corresponding drop in leverage, coupled with steady cash flow coverage improvement, clearly point to an improving credit profile.

<answer>Improving</answer>