Honestly, I think this sort of thing shouldn't happen.
I think we all know that right now J4 is pretty dominant in the jungle, to ridiculous levels. The thing is, although I hate him and hope he's banned every game, he actually isn't that bad skill-wise. He may need a few utility nerfs considering he's got a ton of CC and a bit of mobility, but we've already proven with Lee Sin that Riot would rather nerf anything but the mobility of a champ (health regen nerfs... seriously?). Basically, the thing that pisses me off is when a champion is capable of building close to no damage, yet still delete you in no time flat. Most J4's rush the warrior enchantment, then literally build straight tank for the rest of the game. regardless of the fact that he literally only has one damage item, he can still three shot adc's and some supports.
The same goes for the other way around, if a champion goes straight damage, they shouldn't be tanky. Now, I'm ok with certain passives giving damage from building tanky (Rammus, Galio, Singed, etc.) but when a champion is tanky literally because of their base stats only, it kind of makes me mad.
Basically, the point of this post is just to say that champions should be what they build. If a person builds straight damage, they should be just that. If a person goes straight tank, then they should lack damage. There's no solid good reason (at least relating to the identity of J4 as a champion) that a champion should be able to build one damage item and delete people with no struggles.