I'm having trouble thinking of champs that can outburst smite through Baron's 40% magic damage reduction from MR. I guess Veigar could, especially if he timed his Q and W to land at exactly the same time, but that is about it for instant ability combos that deal over 1k damage through 70 MR.
Ziggs with all four abilities which can technically be timed to all land at the same time (W > R > Bouncing Q > E > W activate) but that involves nothing in his way and roughly 2 seconds of standing next to Baron to pull off.
Maybe Annie? If she was going full AP stacking her Q + R might beat it, but she can't land more than 2 spells instantly so I doubt it.
I could see a Viktor pulling it off with excellent timing, but like ziggs the window has to be very exact and requires the setup of a Q > E, then getting the enhanced lich bane auto as he ults and the second E hits. Like Ziggs this involves dealing damage to Baron at a very exact time where it then falls just outside of the 1000 HP range.
Velkoz? If he Q's so the split hits it at max range, W's so the second explosion hits at the same time plus E for a bit of extra damage and ults just as all the projectiles hits he can probably hit over 1k in a single tick thanks to his passive. The timing on that would be pretty crazy though.
Really only Veigar can easily pull it off, every other mage requires being incredibly fed and having amazing timing/setup. Even something like Kassadin combo isn't instant, and it would probably need the 400 if not 800 mana cost ult to do enough damage. Plus he needs to already be in the bit to add his Q in for the faster burst of Q > R > AA > W, delay, E.
