decoration: const BoxDecoration(
        gradient: LinearGradient(
          begin: Alignment.topCenter,
          end: Alignment(0.0, 0.6),
          colors: <Color>[
            Color(0xffef5350),
            Color(0x00ef5350),
          ],
        ),
      ),
      
      padding: const EdgeInsets.all(16),
      child: Text(
        'Lorem ipsum',
        style: bold24Roboto,
      ),
    ),
  ),
);

Horizontal gradient

background: linear-gradient(90deg, #ef5350, rgba(0, 0, 0, 0) 80%);
}