Two most powerful Dasha systems are KaalChakra & Yogini Dasha...the former is said to be Mahadev explaining Devi timing of events & Yogini is Dasha given by Devi herself. In BPHS Maharishi himself says Kaalchakra is the best & most powerful Dasha system. But most astrologers do not use saying does not give accurate results. However, these 2 dasha system never fail provided you know how to use them. But you need the blessings of Mahadev & Devi to master them.