This happened to me and my company with a F10 retailer in the US long long ago
The reality is, most times you have no options and that whale is your highest likelihood exit
The reality is, this is what being in a market with what are effectively monopolies looks like. You either bully your way to the top or have to deal with being bullied till you can get out.
This is why you need to actually say no to giant enterprise clients until your company is ready enough to weather the multi-year sales cycle with a strong revenue base outside of it, even if those enterprise parties are interested. I think a lot of B2B executives forget this lesson. A sales cycle your company is not ready for could kill it if attempted prematurely, even if it could theoretically close.
It just means spending 12-24 months of time, from everyone including ceo, vps, Product, cto, devs, designers, marketers, to get th contract signed. 24 months of these people's wages is a lot.
The reality is, most times you have no options and that whale is your highest likelihood exit
The reality is, this is what being in a market with what are effectively monopolies looks like. You either bully your way to the top or have to deal with being bullied till you can get out.