much-better.ts

import { Request, Result } from 'express'

export async function showUser (req: Request, res: Result) {
  try {
    const user = await User.findOne({id: req.params.id})
    if (user) {
      res.status(200).send({user})
    } else {
      res.sendStatus(404)
    }
  } catch (e) {
    res.status(500).send({error: e})
  }
}

I think that you meant import { Request, Response } from 'express' on the first line import and on (req: Request, res: Response) function declaration. :)