The best replacement for swain is malzahar.

The best alternatives to swain are rated as following:
★★★★★  malzahar
★★★★★  leblanc
★★★★★  brand
★★★★  ziggs
★★★★  gragas
★★★★  fizz
★★★★  vlad
★★★★  ahri
★★★  orianna
★★★  yasuo
★★★  talon
★★★  karthus
★★★  akali
★★★  zed
★★★  vladimir
★★  rumble
★★  katarina
★★  viktor
★★  kayle
★★  xerath
★  annie
★  anivia
★  swain
★  kassadin
★  kennen
★  ezreal
★  galio
★  syndra
  zyra
  k shine
  passwurdz
  xareth

Your alternative for swain is not listed? Suggest!
Speaking about swain, one probably shouldn't forget about spell vamp.

Other search terms related to swain and their ratings are:
★★★★★ spell vamp
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swain
malzahar
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