Write the best conclusions on a letter?

In conclusion, I want to express my gratitude for your time and attention to this matter. I am confident that with your support and collaboration, we can achieve great success together. Thank you for your continued partnership and I look forward to our future endeavors.

Warm regards,

[Your Name]

Formal Conclusions:

- Yours sincerely, (for a business letter to someone whose name you know)
- Yours faithfully, (for a business letter to someone whose name you don't know)
- Respectfully yours, (for a formal letter to a person in a position of authority)
- Sincerely, (for a professional letter that is less formal than the above)
- Best regards, (for a business letter that is more informal than the above)

Semi-formal Conclusions:

- Thanks,
- Sincerely,
- Best,
- Regards,
- Cheers,

Informal Conclusions:

- Take care,
- Talk soon,
- Keep in touch,
- See you later,
- All the best,