Maw of Mathmortius
Let's say that, by some miracle, a Veigar catches a Kalista in his stun. What would it take for that to kill her? Kalista has 1929 base health at level 18. If she's built Sterak's Gage, her actual health pool goes up to 2329. Maw of Malmortius' shield contributes another 350 (assuming that she has no other MR items) and Sterak's Gage contributes another 699. Once the dust settles, Kalista has 3378 HP of health and shields. She has 85 MR (again, assuming she has no other MR items, runes, or masteries); if Veigar has Sorcerer's Shoes, a Liandry's Torment, an Abyssal Scepter, and a Void Staff, this gets reduced to 5. Once this factors in, Kalista has 3546 effective health against magic damage. Veigar's full combo deals 1030 (+260% AP) magic damage: in order for this to be lethal to Kalista, he needs (2516/2.6): 967 AP.
If Veigar has a Rabadon's, a Zhonya's, and a blue Elixir, plus the four items we assumed he had above, his build gives him 675 ability power once you factor in the Deathcap. This means that he needs to farm the remaining 292, although the Deathcap means that he only actually needs to get 217 AP from the ability itself.
Think about this for a second. A six-item Veigar with an Elixir and every magic pen item in League can't reliably kill a two-item Kalista unless he's also farmed more than two hundred ability power. Is this not problematic to anyone else?

. The effective health ramps up to ~5k (not sure about exact numbers), so any AD champion becomes virtually unkillable by AP since most of AD champs have some way to sustain and heal back, at least that lifesteal from scimitar.
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played his combos right, she'll be dead even with LifeSteal+Fury activated.
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can burst down this Kalista.
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