Many BK players go close and personal with fernando since they think they can blow him up ( ͡° ͜ʖ ͡°). While that is true, fernando has a weapon that is great for pressure. And a pressured BK will go bonkas. Maybe even blow himself up( ͡° ͜ʖ ͡°)
When trying to counter King Bomb with Immortal, make sure to activate your ultimate only after his voice line is over and Bomb King is rolling in your direction, or else he can wait it out and detonate after your ultimate has expired.