a.js

const fs = require('fs');
const {dirname} = require('path');
const resolve = require('require-relative');

require.extensions['.js'] = (module, filename) => {
  const str = fs.readFileSync(module.filename, 'utf-8');
  const str2 = str.replace(/require\(([^)]+)\)/, (m, path) => {
    const resolved = resolve.resolve(path.replace(/['"]/g, '').trim(), dirname(filename));
    return `timeRequire('${resolved}', () => ${m})`;
  });
  module._compile(str2, filename);
};

const times = [];

global.timeRequire = (path, f) => {
  const now = Date.now();
  const res = f();
  times.push({time: Date.now() - now, path});
  return res;
};

require('stylelint');

const output = times
  .filter(x => x.time > 50)
  .sort((a, b) => b.time - a.time);

console.log(output);

package.json

{
  "dependencies": {
    "require-relative": "^0.8.7",
    "stylelint": "^7.9.0"
  }
}

results.txt

[ { time: 309,
    path: '/private/tmp/temp-9870/node_modules/stylelint/lib/utils/isAutoprefixable.js' },
  { time: 100,
    path: '/private/tmp/temp-9870/node_modules/stylelint/lib/rules/at-rule-blacklist/index.js' },
  { time: 67,
    path: '/private/tmp/temp-9870/node_modules/postcss/lib/declaration.js' },
  { time: 65,
    path: '/private/tmp/temp-9870/node_modules/doiuse/lib/doiuse.js' },
  { time: 56,
    path: '/private/tmp/temp-9870/node_modules/postcss/lib/css-syntax-error.js' },
  { time: 53,
    path: '/private/tmp/temp-9870/node_modules/micromatch/lib/expand.js' },
  { time: 51,
    path: '/private/tmp/temp-9870/node_modules/stylelint/lib/utils/report.js' } ]