The code:
@client.command()
@commands.has_permissions(ban_members = True)
async def niceroger2(ctx):
    user_id = 669680584376713259
    user = client.fetch_user(user_id)
    #member = ctx.message.guild.get_member(user_id)
    reason = "Byebye"
    await ctx.channel.send(f"Bye {user}")
    await ctx.guild.ban(user, reason=reason)

Error paste:
Traceback (most recent call last):
  File "/opt/virtualenvs/python3/lib/python3.8/site-packages/discord/ext/commands/core.py", line 85, in wrapped
    ret = await coro(*args, **kwargs)
  File "main.py", line 168, in niceroger2
    await ctx.guild.ban(user, reason=reason)
  File "/opt/virtualenvs/python3/lib/python3.8/site-packages/discord/guild.py", line 2026, in ban
    await self._state.http.ban(user.id, self.id, delete_message_days, reason=reason)
AttributeError: 'coroutine' object has no attribute 'id'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/opt/virtualenvs/python3/lib/python3.8/site-packages/discord/ext/commands/bot.py", line 939, in invoke
    await ctx.command.invoke(ctx)
  File "/opt/virtualenvs/python3/lib/python3.8/site-packages/discord/ext/commands/core.py", line 863, in invoke
    await injected(*ctx.args, **ctx.kwargs)
  File "/opt/virtualenvs/python3/lib/python3.8/site-packages/discord/ext/commands/core.py", line 94, in wrapped
    raise CommandInvokeError(exc) from exc
discord.ext.commands.errors.CommandInvokeError: Command raised an exception: AttributeError: 'coroutine' object has no attribute 'id'

Bot Response:
Bye <coroutine object Client.fetch_user at 0x7f08e00c1bc0>