There is no further tasks you need to accomplish. You can achieve the Gate-A good ending by terminating all Class-D's and Chaos Insurgents. Good Gate-C ending will result in a helicopter coming to pick you up and take you away while the site is put on quarantine. Bad Gate-C ending restarts the game due to no helicopter coming to save you. Good and bad Gate-C ending will depend on what endings you previously had. The bad Gate-B ending will occur if you don't stun 682 in time or the warheads go off. The good Gate-B ending will occur if you stun 682 with the warheads off.

SCP-106 will slowly rise up from the ground and start walking across the bridge to be stunned into its pocket dimension by the H.I.D. The bad Gate-A ending will occur when you have not terminated every CD in the facility or re-contained any of the SCP's. ' Nothing else really happens with this ending and Gate-B ending will play after. The good ending for Gate-A will have a Class-D, (D-9341 from SCP containment breach.) that escaped from the main door by the elevator with his hands up, there will be an audio clip that plays telling the Class-D ' Stop right there. There is a bad and good ending for each gate and requires tasks to get them. There are two Gate-A endings, two Gate-B endings, and two Gate-C endings. Inside of NTF mod, there are 6 different endings for 3 different gates.

Here you can find the good and bad endings of the game and what happens during them.

Scp gate a ending