After graduating and finishing a good apprenticeship of 2 years where i ended up being in charge of a refactoring project (I started as a software engineer and became project lead), I stayed in the same consulting firm and landed a job in Switzerland with a lot more responsibilities in terms of project size, budget, teams etc...
As I was coming from France, my company who switched me to their Swiss subsidiary took advantage of my innocence and offered me an annual wage that's 30% under the average rate for this kind of position (despite my negotiations).
I was aware of this but the opportunity for my career was too great to refuse and I also thought the salary would be sufficient to live well. After a few months of living in Switzerland, I realized this is grossly underpaid and allows me only to "survive".
In order to get some leverage, I started doing interviews and landed an offer at another company. My dilemma is that the job is below the one I have currently in terms of responsibilities, career growth & interest but the offered salary is really great.
Is using this "leverage" I obtained in regard to my current position possible and how ?
Leverage the offered job with my current Business Manager in order to raise the salary to a normal rate and still retain the good position? He might take it badly or be unable/unwilling to raise my salary in which case I would have to go through with this offer in order not to discredit myself.
Go straight to the client and leverage with him directly? I'm a key point in the current project and me leaving would put the project on hold for a lot of involved parties.
Accept the offer and quit? Because even if they accept to raise me to a normal wage, they're going to resent me for forcing their hands and this will corrupt the good relationship we have.
Any advice would be greatly appreciated ! :)