Immunity Shield + Interruption Circles
This is not really difficult to deal with, you MUST however bring a unit with elemental advantage to break the interruption circles. Not being able to doing this will cause a team wipe attack. Thankfully, these interruption circles are extremely low HP and will break easily.
Back Tentacles
Leaving these up will cause a barrage of laser attacks periodically that targets a single NIKKE, they can technically be ignored the higher level you are and if your team composition has constant health recovery.
They have very little HP and are very easy to destroy, but they also respawn constantly throughout the fight. If you are using an element weak NIKKE, and they get targeted, there is a chance they take heavy damage and or die.
Front Tentacles
The front tentacles of Kraken are mainly static during the fight, however they do not remain that way very long. Breaking them is important, even more so if you are bringing an elemental weak NIKKE. After a certain amount of time, the boss will wind the front tentacle up for a swing and deal team wide damage.
Note: This attack pierces cover! It can be blocked by shielding, however… Depending on the stage progression you are capable of reaching, this attack can and will instantly kill elemental weak NIKKE, especially past stage 4 or 5.
Every other tentacle spanwed Kraken will do an AoE attack (changes to every 4 attacks after the Tidal Wave).
After the bosses shell breaks later in the fight, the tentacles lose most of their durability and break almost instantly. This also exposes the core of the boss for full damage, comfort plays a big role in how often you can break the tentacles and target the core for major damage because they will still do the team wide attack.
Tidal Wave
This attack only occurs once during the fight, upon breaking its shell Kraken will submerge into the water after doing so there will be a sequence of White and Red interruption circles on screen, you must break the few in a quick sequence and not break any of the white circles as they have the same durability. Breaking a White circle will cause a team wide attack and wipe.
SBS + S.Sakura Stage 7 with On-Screen Guide about WHAT to do and HOW to do it
Anomaly Interception Kraken Stage 7 Full Auto with Scarlet:Black Shadow, Helm Treasure and Summer Sakura
Tharsis stage 7example run
Anomaly Interception Kraken Stage 9 Clear with Summer Sakura, Scarlet Black Shadow and Rapi: Red Hood by Riza