Your are trying to login to ESXi through direct access console /Putty/ web client?
Starting with vSphere 6.0, account locking is supported for access through SSH and through the vSphere Web Services SDK. The Direct Console Interface (DCUI) and the ESXi Shell do not support account lockout. By default, a maximum of five failed attempts is allowed before the account is locked. The account is unlocked after 15 minutes by default.
Configuring Login Behavior ,You can configure the login behavior for your ESXi host with the following advanced options:
Security.AccountLockFailures. Maximum number of failed login attempts before a user's account is locked. Zero disables account locking.
Security.AccountUnlockTime. Number of seconds that a user is locked out.