(First thing is that you check that all the drivers you have successfully installed in your PC before moving ahead. Do at your own risk,I am no way responsible if you brick/ruin your phone.)
To unbrick your phone download stock ROM and Extract through 7zip software on your desktop.You can also use your backed up ROM(process of backing is explained in my blog) instead of downloading Stock ROM.
Open SP flashtool
Click Scatter Loading then select scatter file from downloaded stock ROM/backed up ROM folder
Click on download -> switch off your phone and connect to PC
Wait till green circle appears