Afternoon! Telegram bot API does not allow bots to delete user's messages in chats where this bot is not an administrator. I doubt there is any bot that would be an admin in all chats where you are. The easiest way is to find the messages you sent in each chat and delete them manually. You can write a bot using the user API, but then the bot must be authorized under your account and you must realize that in this way you temporarily give access to your account to at least one developer who will make the bot.