Are these good alternatives?

[RoseSpring]

I think :

I'll do it no matter what will do.

But I relly need more formal alternatives, so can these work well:

I'll do it at any cost.

// // // at all costs.

// // // whatever happens.

// // // whatever the consequences are.

______________________________________

 

[emsr2d2]

I think :

I'll do it no matter what will do.

But I relly need more formal alternatives, so can these work well:

I'll do it at any cost.

// // // at all costs.

// // // whatever happens.

// // // whatever the consequences are.

______________________________________

In your original quote, you don't need "will do" at the end. You can say "I'll do it no matter what" or "I'll do it no matter what happens".

As far as more formal versions are concerned:

I'll do it regardless of the consequences.

I'll do it no matter what the potential outcome.

Note: If you are required to be extremely formal, then don't use the contraction "I'll", use "I will".