I need to assess whether TenneT Holding B.V. is suitable to issue hybrid bonds based on the financial data provided. Let me analyze key factors that determine hybrid bond suitability.

**Key Considerations for Hybrid Bond Issuance:**

1. **Financial Performance & Profitability:**
- Revenue grew significantly from €5,524M (2021-2022) to €8,299M (2022-2023) - strong growth
- However, the company is consistently unprofitable: Net losses of €340M (2021-2022) and €879M (2022-2023)
- Operating losses are worsening: -€275M to -€976M

2. **Balance Sheet Strength:**
- Total assets grew from €31,200M to €38,509M
- Equity is substantial: €7,713M (2023) vs €7,424M (2022), with equity ratio around 20%
- The company already has hybrid capital of €2,125M (unchanged), indicating prior hybrid issuance experience

3. **Cash Flow Position:**
- Operating cash flow positive: €1,196M (2022-2023) and €5,705M (2021-2022)
- Heavy capital expenditure: €4,424M in 2022-2023
- Investing cash flow deeply negative: -€4,345M
- Financing cash flow positive: €6,556M, heavily reliant on borrowings

4. **Debt Levels & Leverage:**
- Long-term borrowings surged from €12,366M to €19,006M - significant increase
- Total non-current liabilities grew from €15,012M to €21,748M
- Short-term borrowings decreased from €1,339M to €709M

5. **Existing Hybrid Capital:**
- Already has €2,125M in hybrid capital outstanding
- Pays distributions of €57M annually to hybrid capital owners
- This demonstrates market acceptance and track record with hybrid instruments

6. **Parental/Structural Support:**
- Owned by Dutch State - strong implicit government backing
- This is crucial for hybrid bonds as it provides credit enhancement

**Assessment:**

**Positives for Hybrid Suitability:**
- Strong sovereign backing (Dutch State ownership)
- Already has hybrid capital in structure (proven market access)
- Large asset base with substantial infrastructure (PP&E of €26,823M)
- Positive operating cash flows
- Growing revenue base
- Regulated utility nature (transmission system operator) provides stable cash flows

**Negatives for Hybrid Suitability:**
- Consistent net losses and negative profitability trends
- Very high and growing debt burden
- Heavy capex requirements (infrastructure investment)
- Negative comprehensive income
- Worsening operating losses

**Critical Factor - Dutch State Ownership:**
The Dutch State ownership is the decisive factor. Hybrid bonds from state-owned utilities are typically well-supported due to:
- Strategic importance (energy transmission infrastructure)
- Government's incentive to maintain creditworthiness
- Regulatory framework ensuring cost recovery

The existing €2,125M hybrid capital shows the market already accepts this credit. The company's regulated utility status with essential infrastructure assets provides defensive characteristics despite accounting losses.

However, the deteriorating profitability, massive debt increase, and heavy capex needs are concerning. The company is clearly investment-grade primarily due to state ownership rather than standalone financial strength.

Given the state ownership providing implicit support, existing hybrid capital track record, regulated utility nature, and large infrastructure asset base, but offset by weak standalone profitability and high leverage:

<answer>Marginally Suitable</answer>