I'm not gonna lie, I feel that this is happening quite a bit. There are a few players that when I'm against them in WZ's, my packets will spike enormously throughout a match -- as you said -- at critical times.
There is no way -- I don't mean in the "omg, no wai!" sense -- to cause lag to happen on your
machine, besides actually directly breaking into your machine and screwing with the network stack, or hacking the ISP and messing with their switches. If you're seeing a packet spike, that has everything to do w you and your ISP, and absolutely nothing to do with anything that anyone else on the internet is doing. You can believe whatever nonsense you care to, based on whatever irrational standards you enjoy, but that's the reality from a computer / network engineering perspective.