i saw some kid with blackheart and i saw him doing something like j. hk land sj. hk adf hk or something he got like 16 hits with the demons. could someone shed light on this?
thats black hearts form of infinite, which shouldnt be done anymore after the 3rd repetition as it gives them too much meter. but it works in this way… if you hit the guy thats in the air with a FK goblins, they will get captured and will start bouncing, if you hit them again they bounce up again. simply time your jump or hyper jump with FK so that the FK goblins hit them and they will continue to bounce. you can do this to upto 49 hits i believe but then you must finish it as it will end.
easiest way to do this is hit them with cyclops anti air, and super jump FK, dash back, FK, hold forward while landing, super jump FK dash back FK repeat.
or with sonson anti air in the corner, just do the same process.
this one works only in training mode so… its just to get your timing down… without any anti air. LP, LP (becomes a launcher) follow them in the air (while holding back) and FK. it will connect but thats only coz they arent blocking. 
note:
1)his infinite shouldnt be done more than the 3rd repetition, it gives them too much meter for so punitive damage.
2)only do his infinite if you know you can take out their character… or if its down to the very last character and you know that you can finish them off.
3)never finish the infinite with an inferno > heart of darkness, if its cable! unless of course hes in the corner.
hope that helps.
maybe i shouldn’t even bother using it on cable 
Still , you should always try to do this when they have max meter or alot of meter, especially when you dont’ have as much.
you gain almost as much as they do if not the same.
People make too much of the meter it gives them, of course i use cable which means infinite into tag out into ahvb x 2, into guard break next character ahvb x 3
dont’ get random with demons, or predictable, one super jump air dash to combo or super jump into ahvb will leave you huritng, but that doesn’t mean yous houldn’t use it, it’s still good and it does alright damage for me, i almost always get the tag out though so maybe that’s why it seems good to me.