"Of the so-called big-five tech companies in the US, Amazon is the only one without a messaging platform." https://chime.aws/
But it's not really. It's primarily focused around text, and chime is around videos and meetings. That's the use case. Chime is built around meetings. Slack is built around chat.
Disclaimer: Work for AWS.
Chime is definitely better than Lync, but I stand by my statement that it's not very good at text. It's missing basic UI features like threading or merged comments, profile pictures/icons, not to mention more advanced integrations.
I love using it for meetings... but text functionality is still lagging behind Slack, or even Mattermost (also used within Amzn)
Disclaimer: Also work for AWS.