Like the person above stated, there is no best major for getting the most competitive GPA (even if you think there is, there isn't). If you would prefer sociology or psychology (which are great courses), then go for one of those. Challenge yourself, do something you want to do, and enjoy it. No one on this website can give you the answers you're seeking. It also seems like you haven't done much of your own searching, have you tried googling what programs are available at the different schools in NS?
Have you reflected on why you found engineering hard? Or why you weren't able to obtain a 'competitive' GPA with the degree you already have? (Maybe you didn't realize you wanted to go to med school and it was too little too late, and that's fine!).You said you "do not want to be again in hard undergrad once again after the engineering", which suggests that you're not willing to put in the effort it takes to get into med school, let alone actually study medicine (which is very hard and just so happens to be classified as an undergrad degree). Your post comes across like you're expecting to go into an "easier" second undergrad, do really well, and then get accepted. You have a long road ahead of you, so be prepared to work! If you're not willing to work hard to get into med school, then you're not setting yourself up to succeed once you get in. I apologize if you're just learning English, but I'd suggest taking some English/grammar courses to improve your writing (it really impresses admission people when you know how to write properly).