My first thought was 700 Remington of unknown caliber, but [deity of your choice] a .700 rifle, you could kill the planet with that. Shot placement is key.
I remember years ago seeing Jim Carmichael's article in Outdoor Life with a multiple exposure photo showing him firing an H&H double rifle chambered in .700 Nitro Express.
The final frame showed the barrel pointed well beyond fully vertical!
And keep in mind that Jim is no novice shooter.