Two weeks ago I joined a new company and during the hiring process I used a competing offer to increase the proposed salary.
Now that competing offer from the other company has increased to almost 2x the offer that they initially proposed. And now I want to join them for financial reasons and leave my current job during the probation period. Note that my probation period is 3 months.
How would I approach the resignation and what reason should I give, noting that my current job can easily find out that I left for the original competing company? I don't know if this will be considered unethical? This is only my second time joining a new company.
Edit: I've read all comments thank you everyone for your feedback was very helpful. I want to clarify some things about my situation. After I accepted my current job, I informed the competing offer that I am no longer interested in their offer since I've accepted another more suitable one. What happened is after about 2 weeks they sent me the competing offer with better pay and benefits without me negotiating, which made it more enticing for me and my situation, hence why I decided on the resignation.
I am not in the US, the rules here are during the probation period the employer could let you go at anytime without giving any reasons and without any compensations. However, if the employee wishes to leave then they must submit an official resignation with one month notice period with pay.
What I did is that I submitted my resignation with the month notice and showed my gratitude for the opportunity. I don't want to burn any bridges or try to negotiate the offer further. Right now they accepted the resignation, however the HR are calling me unethical which is making me feel uneasy.
The competing offer does not know that I already signed a contract and that I already started working there. The competing offer's salary is about 85% more than my current job salary, with better health insurance coverage. The competing company does not know the details of my current job, salary, benefits, etc..