A team of mediocre characters with S-rank and Z-rank equipment will beat a team of Ultra characters with A-rank gear. Use the "Guaranteed Upgrade" feature and slot removers (earned via Co-op) to max out your equipment. This is a 100% legal stat boost.
If you love Dragon Ball , you are doing yourself a disservice by not playing this.
Complete a "verification" step, which usually requires downloading and running two other free apps for a set period.