I honestly hate itach hes cool but overated asf i I'm a madara man personally but tendo just as no way of beating him Yada mirror can change any and all properties of itself in order to nullify what's coming at it even gravitational fields which is all tendo pain can do a chibaku tensei isn't stopping itachi his susanoo is fully capable of breaking out. Also totsu blade is literally an instant one shot no matter who you're so unless you either A. Counter one or both of those or B. Outstat/outhax him to the point the Yada mirror is effectively useless and the totsuka blade can't hit you and tendo pain does neither of those things they're very relative meaning the odds are in itachis favor