@mixin margin-bottom($margin: $default-margin) {
  margin-bottom: $margin;

  @include breakpoint('medium') {
    margin-bottom: #{$margin * 1.5};
  }

  @include breakpoint('large') {
    margin-bottom: #{$margin * 2};
  }
}

@mixin margin-bottom($margin: $default-margin) {
  margin-bottom: $margin;

  @include breakpoint('medium') {
    margin-bottom: #{$margin * 1.5};
  }

  @include breakpoint('large') {
    margin-bottom: #{$margin * 2};
  }

  > :last-child {
    margin-bottom: 0;
  }
}

Remove margin from last child on elements with bottom margin mixin
:lipstick: Remove margin from last child on elements with bottom margin mixin
