Viktor Siphon Power skill's (Q) secondary magic attack can shoot up to 3 times to inhibs
With Viktor if you Q (Siphon Power) an enemy mob then the next 3 basic attacks will do be converted magic damage to the inhibitors instead of the usual 1 attack. I have tried this 3 times in one game and all 3 times the animation, sound and the increased damage was done.
Was using Creator Viktor skin and here is the link to the match: http://matchhistory.euw.leagueoflegends.com/en/#match-details/EUW1/2649773189/205071112?tab=overview
Sejuani used to be able to do this with her W's duration to deal bonus damage on structures, but Riot removed it 'cause "broken" or because it was unintentional, I do not remember. I do it all the time to melt structures faster when I use Viktor. You can proc the bonus damage as long as the duration holds. ¯_(ツ)_/¯