They are not fast creatures but they do like to get up and personal. If one of these locks onto you it would be best to pull out a high damaging close range weapon [shotgun] so that you can get a good amount of shots on and kill it with ease. The other method would be to use a sniper from long range and take the creature out from there but be aware of the long ranged acid attack.
The purple 'eye' is the critical area and does large amounts of damage. Usually results in a one-shot-kill. Striking to the head by splash damage weapons can provide enormous amount of damage (up to 99999).