We can disable the Lightning Locker Service by lowering the API version to 39 or earlier in Salesforce Lightning Components.

Salesforce Lightning Locker Service is a powerful security architecture for the Lightning components. Locker Service enhances the Salesforce security by isolating Lightning components that belong to one namespace from components in a different namespace. The Salesforce Locker Service also promotes best practices that improve the supportability of your code by only allowing access to supported APIs and eliminating access to non-published framework internals.

If we downgrade the API version to 39.0 or earlier, then

1. It downgrades the Lightning Component security.
2. Features/Functionalities introduced after Spring’17 release cannot be utilized since the API Version doesn’t support it.
3. Please don’t mix the Component API Versions.
For consistency and ease of debugging, we recommend that you set the same Salesforce API version for all custom components in your app, containment hierarchy (component within component), or extension hierarchy (component extending component).
If you mix the API versions in your containment or extension hierarchy and Lightning Locker is enabled for some components and disabled for other components, your app will be harder to debug.
https://developer.salesforce.com/docs/atlas.en-us.lightning.meta/lightning/security_ls_api_version_mix.htm
4. Salesforce Lightning Locker Service also prevents the Cross Site Scripting (XSS). So, your Lighting component becomes prone to it.