grammY makes it easy to create Telegram bots. Both for beginners and at scale. You want grammY because it is easy to use. It is very powerful and always up to date. It has the best documentation in town. It is extremely efficient and scales up effortlessly. It has a thriving ecosystem of plugins, a friendly community chat, seamless integrations with web frameworks and databases, and so much more.
Using this plugin-based framework, you can instantly start working on the *brain* of your bot (irc bot, chatterbot, robot, ...). With support for db, irc, logging and programming-language independent plugins, users can easily enhance the functionality.
A chatbot framework currently implementing the ErkiTalk and irc protocol. By specifying parsers for the server's input one can easily create custom bots (if one can program in java of course ;).