TL:DR - Shadow is to strong to be a 240 gold blue tower , needs to either have price and quality raised, or its indefinite increase in dmg needs to cap or be nerfed.
I know there are many actual towers that are meant to "carry", With the Changes to Iron man , and having wedding rings you can have 3 carry towers pretty much (potion up the ones wearing bands, and Items are for buffs for iron man over potions) but I have run into many problems with this and cannot even come close to the leaderboards because i do not use the Shadow.
I have tried many combinations avoiding using the shadow and cannot compete because of the shadows Bonus DMG stacking.
Towers i have tried :
Frog - Its ability seemed Good and would be amazing, but i do not think its ability applied with reaver, or proporly stacked (you think at 99, and avg dmg of 1m and .1 attack would be able to destroy challenges/horsemen) but no it is not.
Black widow - is an amazing tower, but seemms to just lack the "umph" needed to carry in the long run (with luck u can hit lvl 500, but not to far in challenge cus of the 1 range)
Iron man - Great carry tower if you are lucky enough with Drops to feed his Never ending Lust to be strong, but will not fully match a shadows bonus dmg.
Electric Chair - Very difficult tower to start with, can do good with it if it gets moving, but in the end will fall short in long run.
Scarecrow - Could be an amazing tower if built in the back on a genesha, otherwise again like the chair difficult to get going because of slow atk speed.and in the end fall short on bonus waves cus of Endless mobs and no real time to build up crows.
Other towers i have not tried.- NEver tried their speed/dmg/ "skills" are not interesting.
If a ladder reset does occur , with the Knus change and Olaf i suggest a Nerf to the Shadows % dmg as well to bring it in check with other "carry" towers since i feel it is even stronger than purples (and its a blue u can roll at lvl 1!)