I have received another offer from Company B that is substantially better than my current offer from Company A (which I have signed) in terms of compensation, responsibilities and team. I am curious to know what are some ways to approach this.
Are there any pitfalls I should be aware of, in the above scenarios? Please share your experiences, if you have done this in the past.
If the offer from company B is substantially better, you should take it. Your employment in the US is at-will, so there's absolutely nothing illegal about reneging. (You'd likely have to give back any signing bonus)
However, you're right you may potentially burn bridges. Two things to note:
#2, I've never seen that happen. Once you've signed the offer and joined a company, you lose almost all your leverage.
What is the best way for me to renege the previous offer without burning bridges?
There is none. Companies (understandably) hate reneging. Giving an interview + extending an offer takes a ton of human resources (more than you spent going through the loop), so it really hurts when you re-neg.
Did anyone here show a competing offer to Company A (after signing) and try to re-negotiate or move the needle? Has it worked for you, if you did this in a polite manner?
As Rahul mentioned, this won't work. You have already signed.
Congrats on the offer! If you're able to secure more offers, here's our negotiation playlist: [Taro Top 10] Pay Negotiation