This could cause grave consequences.

这会造成严重后果。

This large rain could have grave consequences.

这场大雨会造成严重后果。

This heavy rain could have grave consequences.

这场雨会造成严重后果。

These events could have grave consequences for all of us.

这些事件可能给我们带来严重后果。

Any deficiency or cursoriness of the management will lead to grave consequences.

任何管理上的不足和疏忽，都会对活动造成不可估计的后果。