Do ADHD children ever become very aggressive?

Yes they can. Although many adhd children are not aggressive, their impulsivity and high levels of physical activity can set them up for situations in which they or others become upset, leading to aggression. In toddlers with adhd, the most common cause of referrals in aggression in the preschool setting. Older children may be teased and scapegoated, which may to anger and aggression.
Yes. Some children or young adults with adhd may become aggressive. Sometimes that indicates an additional diagnosis needs to be considered and possibly addressed. Some adhd children and young adults won't be aggressive, or not physically aggressive. Children and young adults with adhd are more at risk than the general population for other mental health diagnoses.
Possibly. Agression can occur in the life of any child. However, it is not a natural feature of ADHD. Consider the psychosocial and environmental features linked to this behavior.
Yes. Children will adhd often have issues with impulse control which can lead to inadequately processing an appropriate response to an action. This can lead to an aggressive reaction. In addition, children with adhd may have difficulty adjusting to new situations and odd (opposition defiant disorder) leading to more confrontational situations.