I would usually break code like this out, but I was tinkering about and was trying to make a lot of it inline. Had fun writing it though!

major-ver-check.js

// Setup npm packages w/o variables
(({ lstatSync, readdirSync }, { join }, check, chalk, { table }, ora) =>
  // Create lambda and immediately call it later
  ((source, getPkgName, spinner) =>
      // Wait for all Promises to finish running. Promise.all returns an array
      void Promise.all(
        readdirSync(source)
          // Give me the fill paths of the items
          .map(name => join(source, name))
          // Only give me directories
          .filter(source => lstatSync(source).isDirectory())
          .map(pkgPath =>
            // Check for package data
            check({ cwd: pkgPath })
              .reduce((prev, { get }) =>
                // Make a lambda that's immediately called in order to avoid duplication of logic
                ((pkgList, pkgName) =>
                    void console.log(`\nGot data for ${pkgName}`) ||
                    pkgList.length ? [
                      () => console.log(chalk.bold(pkgName)),
                      () => console.log('\n' + table(
                        [
                          // Add header text and concat with pkglist to display properly in a `table`
                          [
                            chalk`{bold Package Name}`,
                            chalk`{bold Dep Type}`,
                            chalk`{bold Old Package}`,
                            chalk`{bold New Package}`
                          ].concat(pkgList)
                        ]))
                      // Otherwise return `prev` in order to not print anything about this data
                    ] : prev
                )(
                  // Get the `packages` data from the `check` call to return as the first arg
                  get('packages')
                    // Only give me packages that have a `major` spec bump
                    .filter(pkg => pkg.bump && pkg.bump === 'major')
                    // Map to an array of strings to print later. Made array as we want it to match `table` console call
                    .map(({ moduleName, latest, devDependency, packageWanted }) => [
                      chalk.bold(moduleName),
                      devDependency ? chalk.bgYellow`Dev Dep` : chalk.bgGreen`Main Dep`,
                      packageWanted,
                      latest
                    ]),
                  // Pass `getPkName` as second arg
                  getPkgName(pkgPath)
                ), []
              )
              .catch(
                // If there's an error, it means that the data we're looking for doesn't exist.
                () =>
                  // Use lambda to be immediately called with the package name to reduce data duplication
                  // Use `void console.log ||` to console log and return the array of lambdas in one line
                  (pkgName => void console.log(`\nGot data for ${pkgName}`) || [
                    () => console.log(chalk`\n{bold.bgWhite ${pkgName} does not have a package.json}`)
                  ])(getPkgName(pkgPath))
              )
          )
      )
        // Once all that is done, for each package, for each function in that package data, run
        .then(arr => void arr.forEach(val => val.forEach(a => a())) || spinner.stop())
        // If there was an error (somehow?) then handle it and stop the spinner
        .catch((e) => console.error(e) || spinner.stop())
    // Call top level lambda with
  )(
    // The string of the current path
    process.cwd(),
    // A lambda that, given a string, will split my `/` and return the last item
    path => path.split(/[\/\\]/).find((_, i, a) => i == a.length - 1),
    // Start a process to display a loading spinner
    ora('Searching packages').start()
  ))(
  require('fs'),
  require('path'),
  require('npm-check'),
  require('chalk'),
  require('table'),
  require('ora')
);

Thank you for not actually making it literally a one-liner

@rusher2004 I gotchu

((m,f,x)=>(({lstatSync:l,readdirSync:r},{join:j},c,h,{table:t},o)=>((s,g,p)=>void Promise.all(r(s)[m](n=>j(s,n))[f](e=>l(e).isDirectory())[m](k=>c({cwd:k}).reduce((h,{get})=>((pl,pn)=>void x(`\nGot data for ${pn}`)||pl.length?[()=>x(h.bold(pn)),()=>x('\n'+t([[h`{bold Package Name}`,h`{bold Dep Type}`,h`{bold Old Package}`,h`{bold New Package}`].concat(pl)]))]:h)(get('packages')[f](k=>k.bump&&k.bump==='major')[m](({moduleName:b,latest:z,devDependency:v,packageWanted:w})=>[h.bold(b),v?h.bgYellow`Dev Dep`:h.bgGreen`Main Dep`,w,z]),g(k)),[]).catch(()=>(u=>void x(`\nGot data for ${u}`)||[()=>x(h`\n{bold.bgWhite ${u} does not have a package.json}`)])(g(k))))).then(arr=>void arr.forEach(val=>val.forEach(a=>a()))||p.stop()).catch((e)=>console.error(e)||p.stop()))(process.cwd(),z=>z.split(/[\/\\]/).find((_,i,a)=>i==a.length-1),o('Searching packages').start()))(require('fs'),require('path'),require('npm-check'),require('chalk'),require('table'),require('ora')))('map','filter',console.log)

Done by hand