I don't know if this has been mentioned before but i found combo which can deal about 1 bar of damage.
First you need two attack supports, at least one of which has an SB attack. Once your support gauge is filled enough use your SB support or your grab then follow up with Tsunade's mid-air U1 then her grab which results in SB then use either Mid-Air U1 then grab or if they're SB'd close enough U2.
Also this isn't full-proof since they can dodge these attacks and if they jump out of the SB or U1 but this is a relatively safe combo due to most actions having little lag so theres no real risk in trying it.
So it's basically Support>SB>Mid-Air U1>Grab>SB> either Mid-Air U1>Grab or U2.