Apparently you hooligans have no idea what a main tank is compared to an offtank, so i’m here to help, as a main tank main.
Main tanks are space takers, they forcibly take space, by walking into it, reinhardt closes gaps either with a shield while alies shoot, or shatter/charge and brawling to secure his new position.
Orisa is similar to rein, except instead of charge she pulls enemies around either repositioning vulnerable enemies or moving them back as she advances.
Winston is special and can be played as either, but as main tank, he can dive the backline with another hero, offtank or flanker, and take space by effectively crushing the enemy inbetween the two sides of the team. (IF you dive their backline and don’t push them toward your team, you are offtanking, not main tanking. IE, chasing widow around.)
Hammond moves frontline enemies backwards, backline enemies forwards, deters flankers and can make use of piledrive and mines to seriously punish anyone who tries to take their space. (If you are spinning on the point for the whole game, you’re not tanking you’re griefing, making it very hard for your team to actual hit anything. don’t do this.) You can play ball as an offtank, but his main gun really isn’t effective enough for it, so you’re pretty much just a budget doomfist.
Now offtanks, offtanks are very easy. They shoot stuff that’s trying to flank/push their team, specifically they’re there to relieve pressure from the main tanks and peel for the supports.
Sigma is NOT a main tank, nothing about his kit takes space except his ult, which really has to be paired up with another ult to be effective.
I’m tired of a guy with 3 hours on sigma telling me what a main tanks job is. It is not my job to stop Tracer running at you, Tobjorn, if I do stop her, it’s because I needed 8% ult charge for my shatter.
TL;DR: A main tank is not something with a shield.
P.S I’ve never played above plat so Maybe in diamond hammond is an offtank but that just seems dumb.