BotStar is probably the best chatbot builder to hit AppSumo to date (I bought almost every bot app offered on AppSumo in the past 2 years). It's a very well designed and mature app that offers everything necessary to build powerful bots for multiple purposes.

It supports websites and FB messenger. It has human takeovers, drip campaigns, broadcasts, inboxes, supports complex bot designs, and behaviors, etc, etc. The list goes on.

The UX is very well thought out to minimize clicks and to always know at which stage you are in your workflow. Few apps do this very well and BotStar ranks high amongst them. I would hire their UX person on the spot.

The possibility to restrict which features within a bot each collaborator can access makes this a must buy for any agency thinking of offering bots to their clients.