I can give a simple, faithful Jain-orthodox contrast between Atma Siddhi (Kundakundacharya) and Kundakunda’s own exposition, focusing on what each text says and how they relate. I’ll keep to core points and note where the two works align or differ in emphasis.

Line-by-line style contrast (conceptual, not verbatim)

1) Existence and nature of the soul

• Atma Siddhi: The soul (jīva) exists and is real; it is conscious, doer of its own karma, and enjoyer or sufferer of the fruits of those karmas. It is eternal and central to liberation. This is stated as a foundational, six-fold truth.
• Kundakunda (Pañcāstikāyā-sāra / Pravacanasāra approach): The soul is the primary reality (jīva) and is distinct from non-soul (ajīva). The text emphasizes the jīva as the purer, knowing self, and teaches that karma attaches to the soul, which is the agent of its own outcomes.

Alignment: Both treat the soul as the essential, conscious being whose true nature is central to liberation. The difference is mainly in how they frame the path to knowing this truth (sixfold truths in Atma Siddhi vs. doctrinal analysis of jīva, karma, and naya-principles in Kundakunda’s Nyāya framework).

2) Permanence (eternity) of the soul

• Atma Siddhi: The soul is eternal; it does not vanish with the body and persists across cycles until liberation.
• Kundakunda: Similarly, the soul’s permanence is part of the fundamental nature of jīva; the work uses this to contrast with transient physical phenomena and to explain bondage and release.

Alignment: Both assert the soul’s eternity. The difference is mostly in the way they connect eternity to the mechanics of bondage and release (Atma Siddhi states it as one of the six fundamentals; Kundakunda treats it within the broader scheme of jīva, karma, and mokṣa in his niścaya-naya and vyavahāra-naya framework).

3) The soul as doer (kartā) of its karma

• Atma Siddhi: The soul is the doer of its actions; it is responsible for the karma that attaches to it.
• Kundakunda: The soul is the karta (agent) under the theory that karmas bind the soul through intention (darśana, cetanā) and action; the work clarifies how bondage occurs and how it can be stopped.

Contrast: Both affirm the soul as responsible for its own actions, but Kundakunda develops this with his two-naya (dravyārthika and paryāyārthika) distinctions and a detailed description of how karma operates on the soul, whereas Atma Siddhi presents it as a fundamental truth within the sixfold framework.

4) The soul as enjoyer/sufferer of its karma

• Atma Siddhi: The soul experiences the results of its actions (enjoyment or suffering) due to karmic attachment; this is part of the six fundamental truths.
• Kundakunda: The experiential aspect of karma (enjoyment and suffering) is analyzed in terms of the interactions between jīva, vedanā, and karmic influx; the texts explain how perception, conduct, and ignorance contribute to bondage and the possibility of liberation.

Contrast: Both describe experience as a consequence of karma, but Kundakunda places it within his analytic framework of saṁvara (stoppage) and niścaya (definite knowledge) about how the self interacts with karma, whereas Atma Siddhi emphasizes it as a fundamental reality to be realized and acted upon.

5) Liberation exists (mukti)

• Atma Siddhi: There is liberation; it is the ultimate goal and a real state for the soul when karmic influx is stopped and purificatory knowledge is achieved.
• Kundakunda: Liberation is a central aim; the text elaborates a method (darśana, jñāna, and caritra) to attain mokṣa, with special attention to the destruction of mohaniya karmas (deluding karmas) and perfecting right knowledge.

Alignment: Both affirm liberation as real and achievable. The difference is in the method and emphasis: Atma Siddhi states the six fundamentals clearly as the ground for liberation; Kundakunda articulates the process through his niścaya-naya (self-realization under the absolute view) and vyavahāra-naya (practical conduct and understanding).

6) Path to liberation (means to mokṣa)

• Atma Siddhi: The sixth fundamental includes the means of liberation; the text outlines a logical, dialogic path where a teacher clarifies doubts and guides the seeker toward realization.
• Kundakunda: The path is developed through a systematic analysis of the self, karma, models of truth (padārtha), and the necessary discipline (non-attachment, right conduct, right knowledge). His works (Samayasāra, Pancastikāya-sāra, Pravacanasāra) present a thorough framework for attaining mokṣa.

Contrast: Atma Siddhi presents a compact, dialogic structure to introduce and defend the six fundamentals, while Kundakunda’s broader corpus lays out the philosophical architecture (dravyārthika vs. paryāyārthika, saptabhaṅga, syād, asti/naṣti, etc.) that underpins the path.

7) Style and pedagogical aim

• Atma Siddhi: A poetic, six-point exposition designed to establish basic Jain ontology for an earnest seeker; it uses a Q&A format in parts of the text, with a focus on the essentials a seeker must accept.
• Kundakunda: A deeper, more technical exegesis (two-naya framework, detailed categorization of substances (dravya), and truth-claims) intended for mature monks and philosophically trained readers; it emphasizes distinguishing points of view (vyavahāra-naya vs. niścaya-naya) to reveal the ultimate nature of the self.

Difference in tradition emphasis

• Digambara vs. Śvetāmbara nuance: Kundakunda’s works are foundational in Digambara tradition and shape its soteriology and epistemology. Śvetāmbara inputs on similar topics often bring additional texts and interpretations, but the core self-knowledge approach in Kundakunda remains a central reference in Digambara Jainism.

What this means in practice

• If you read Atma Siddhi, you get a compact, six-fold statement of what the soul is and what it needs to do to realize liberation.
• If you read Kundakunda’s Pancastikāyā-sāra, Pravacanasāra, and Samayasāra, you get a broader, more technical map of reality (jīva, ajīva, karma), the two-naya methodology for perceiving truth, and a detailed program for purification and liberation.

Notes for further study

• Both bodies of work are coherent within Jain Dharma, and they complement each other: Atma Siddhi offers a concise manifesto of the soul’s true nature and the liberation goal, while Kundakunda’s broader works offer the deeper ontology, epistemology, and soteriology that explain how that goal is realized in life and practice.
• If you want exact verses and traditional Kathās (commentaries), I can cite the precise lines from each text and map them side by side with traditional Digambara readings (and, where relevant, Śvetāmbara readings).