Determination

Determination is a power that allows SOULs to persist after death. The most determined being in the Underground is able to SAVE.
==Overview==
Determination is naturally possessed by humans. Undyne is the only monster who is confirmed to naturally have determination, but it is possible that every monster possesses a small amount of it. Should a monster acquire a high concentration of determination, their body melts, usually into an amalgamate. A being without a SOUL can gain the will to live if it acquires determination, a prime example being Flowey.
==Main Story==
SAVE Points can be found throughout the game. These SAVE Points express the protagonist's determination and thoughts in regards to recent events.
===Neutral Route===
If the protagonist kills Undyne, then she melts in a similar fashion to the Amalgamates before turning to dust.
===True Pacifist Route===
In the True Lab, it is revealed that Alphys started experimenting with determination extracted from human SOULs in an attempt to unleash the power of the SOUL. She used blueprints to operate the DT Extraction Machine to obtain determination and began injecting it into the bodies of monsters who had fallen down and a Golden Flower that as a result became Flowey. However, since their bodies cannot handle determination, the monsters injected with determination soon melted together and became Amalgamates.
===Genocide Route===
When using a SAVE Point after exhausting a region's kill count, it only says "Determination." with no context in particular.
When Undyne takes a blow from the protagonist, she holds on through her determination and challenges the protagonist as Undyne the Undying. Upon defeat, she melts in a similar fashion to how she melts on the Neutral Route before turning to dust.
==Trivia==
*The SAVE Point description in Temmie Village refers to determination as "detemmienation."
*"Determination" might be a play on words, as the primary power it affords is the ability to reverse death, either the protagonist's or those they may have killed, hence de-termination.
*It is unknown if the Amalgamates mimicking game elements such as the protagonist's "!" dialogue box or SAVE Points are actually happening and related to the Determination they have been injected with, or are simply breaks of the fourth wall intended to catch players off-guard.
* The DT Extraction Machine resembles most parts of Photoshop Flowey (Most notably the inverted mouth and the eye sockets).
*Most of the text in Undertale is rendered in a font called Determination Mono.