Swords are all about the element of Air. Air is the element which brings clarity but when adversely affected it can be mental unstability and sorrow.
3 of swords can be a harsh card in a reading. It comes up when one is expected to experience piercing pain, the pain usually is on emotional level rather than physical level. Its acute pain which can pull down the mental stamina of a person.
Knight of sword is a aggressive person who doesnt have any patience they can be impulsive and indecisive. They do not fear hurting anybody because they are quite self centered. The 3 of swords alongwith this card surely indicates bad fight which is going to inevitably hurt the person and bring them down emotionally.
Alongwith hurt and pain 3 of swords also indicates sorrow, disappointment, betrayal and rejection.
In an another reading the 3 of swords came up with Death. This can be a deadly combination. With betrayal and sorrow the card of permanent change comes up. So definitely the situation will hurt for a long long time.
Death is always a card of change and those change which will usher in something new but it will permanently end the earlier path. So if you were working for a particular organisation and the Death card comes up in the reading it could literally mean that you will be loosing that job and permanently but that wont be the end of the road.
It will bring in change and transformation for you. Though you may hurt for a longtime but the change wiill help you pursue better things which can help you grow emotionally and spiritually.
Its always necessary to be cautious and tread carefully when the 3 of swords come up in a reading. Even wiser to take a different reading and to ask tarot how to avoid the impending 3 of swords and if it cannot be avoided then counter measures to deal with it in positive manner.